Could the federal government ban people from drinking coffee? Which amendment does this statement violate? The federal government refuses to allow anyone to drink coffee.
None. The federal government is allowed to prohibit coffee drinking under its power to regulate interstate commerce. Prohibition would not have required a constitutional amendment under modern constitutional jurisprudence either. By analogy, this would be no different (constitutionally) than a law prohibiting putting lithium in sodas (something that used to be done in 7 Up) or putting cocaine in sodas (something that used to be done in Coca-Cola). Conceivably, the law might have to allow a religious exemption in certain circumstances under the 1st Amendment's free exercise clause, but while many faiths prohibit drinking coffee (most notably, offshoots of The Church of Jesus Christ of Latter-day Saints), none of which I am aware require it as a matter of religious doctrine sincerely espoused.
Since you asked, and it's a perfectly legitimate question, here's why it doesn't violate the Fifth Amendment (from Garner v. US): The Fifth Amendment doesn't say "you can't be made to say anything that hurts you." It says "no person...shall be compelled in any criminal case to be a witness against himself." The only time Fifth Amendment protection applies is if you are being forced by the government to make a statement that could open you up to an accusation or conviction of a criminal offense. It's fairly broad (if it would help prove any aspect of the charge, you can claim immunity), but it's also restricted (you can't claim it unless it really would tend to incriminate you). That means that you could only argue the Fifth Amendment if your tax return might help prove a criminal case against you (the fact that disclosing income leads to you needing to pay tax does not qualify as "self-incrimination"). But the amount of income is not one of those things that might incriminate you -- you can get income through all sorts of ways. The thing that is incriminating is revealing the source of the income, and you can claim Fifth Amendment privilege for that. So: The only time you could possibly claim privilege is if you were being forced into a statement that might tend to incriminate you in a criminal proceeding. A statement that makes you liable for tax doesn't mean it might incriminate you. Filing an income tax return isn't inherently incriminating. The fact that you have income not included in any other part of the return (illegal income goes under "other income") doesn't imply you've committed a crime -- lots of people have other income. The amount of income can't be incriminating. The source can be, but you can claim Fifth Amendment privilege for that if it might incriminate you. And lawful income under "other income" still might give rise to a reasonable fear of prosecution, so the fact that you're justified in claiming Fifth Amendment privilege in source of income doesn't mean you're guilty of a crime. Note that there are cases where you are flat-out exempt from filing tax returns under the Fifth Amendment: Marchetti v. US and Grosso v. US found that registration and tax on gambling could be blocked by a Fifth Amendment claim, which didn't even have to be asserted at time of filing, because merely filing the special return would establish you as a gambler (heavily regulated/often criminalized at the state level). The difference with the normal income tax form is that everyone (just about) files one, and so filing it doesn't mean you're a criminal. If there was a separate line along the lines of "Income from Illegal Drug Sales," that might be one thing (anything other than $0 is inherently incriminating). But all the questions are broad, and have many legal sources of income associated with them.
Is this illegal? No, subject to some possible narrow exceptions discussed below. Do the social media companies have a duty under the First Amendment to not censor users? No. Indeed, usually, there is greater liability exposure for failing to censor content, for example, by failing to honor a "take down notice" under Title II of the Digital Millennium Copyright Act based upon an alleged copyright violation, or for failure to censor content related to potential sex trafficking. The First Amendment to the United State Constitution (which applies to state and local government via the 14th Amendment to the United States Constitution) is a limitation on the power of governmental actors only. This said, some state constitutions, such as California's, provide free speech protections not just from government action, but also in spaces that are privately owned, but are open to the public and constitute de facto public forums. The authority of California to expand its state constitutional protections to these private settings was confirmed by the U.S. Supreme Court in the case Pruneyard Shopping Center v. Robins, 447 U.S. 74 (1980). It is conceivable that these doctrines could be expanded to public Internet forums in the case of California based social media companies (e.g., Facebook has its headquarters in Menlo Park, California; so does its sister platform Instagram; LinkedIn is based in Sunnyvale, California; and Google is based in Mountain View, California). There are also laws that limit how employers can regulate employee speech in a labor relations context, although most of them don't have constitutional dimensions. It is conceivable that these doctrines could limit social media platform's authority to limit some kinds of speech by their own employees, or in situations where the social media platform looked like it was acting as a mere agent of some other employer controlled by that employer for all practical purposes. There has also been litigation related to free speech on social media regarding the rights of governmental account holders to exercise the same kinds of account management that is available to other users, implicating the First Amendment right to petition the government. The social media platform operator is not itself the primary target in these cases, but if it simply implements its terms of service neutrally with respect to all account holders, it could be facilitating a constitutional violation by its governmental account holders and could conceivably be held liable for aiding and abetting that violation of the law by a governmental account holder (in the context of a lawsuit for money damages this is a special subtype of something called a civil conspiracy).
Before the election, can a lawsuit prevent the amendment question from being put on the ballot? No. Generally speaking, the constitutionality of an otherwise procedurally proper ballot initiative is not ruled upon until after it has passed (eliminating the need to rule unnecessarily on the constitutionality of failed initiatives). Of course, if someone tried to put it in the ballot when the existing law conditions for putting it on the ballot were not met (e.g. because a deadline for doing so wasn't met) that could be challenged in court by a party with standing to do so. If passed into the constitution, would a court still have the ability to rule the restrictions unconstitutional? Probably not. The constitution as newly adopted doesn't sound like it would forbid doing that. This seems to be the whole point of the constitutional amendment in the first place and it the amendment to the constition is approved, that requirement is gone.
Governments have power to do whatever their constitutions (written or unwritten) allow them to do. For example, the constitution of Australia provides: The federal Parliament can make laws only on certain matters. These include: ... post and telecommunications; ... The telecommunications power covers VPN and any software that uses the Internet for delivery or communication (i.e. virtually all modern software). In addition the federal government has power over inter-state and international trade (any software that crosses state or international borders) and corporations (any software made, sold or used by companies). If they want to ban a piece of software they have pretty strong constitutional power to do so.
tl;dr My assumption: the U.S. government is considering whether to accept refugees and immigrants (given your Syria comment). The background section talks about State attempts to restrict entry. The answer is nuanced since there are different standards for an entrance decision than there are for someone who is already in the U.S. This is because foreign nationals in their home nations aren't "persons within the jurisdiction of the United States," and so laws like the Civil Rights Act only apply in spirit. What does that mean? We wouldn't expect to see the federal government discriminate based on religion, but we might expect to see decisions made about groups that incidentally share an common religion. This is because the federal government has wide latitude when it comes to alienage---which is just a formal name for policies related to non-citizens. While religion is afforded a high degree of protection, the federal government's alienage policies are governed by the lowest level of judicial scrutiny. This implies a practical challenge: things like religion and national origin can be very difficult to disentangle from questions that pertain to the alienage category. For example, a policy might restrict some group's entry "because of" a particular alienage reason and "in spite of" the fact that most of the affected people happen to share a common religion. Background The Equal Protection Clause U.S. Const. Am. XIV § 1 prohibits States from denying any person within its jurisdiction "equal protection of the laws." The Clause is often applied to the federal government as well, via the Due Process Clause U.S. Const. Am. V. See, e.g. Bolling v. Sharpe, 347 U.S. 497 (1954). In relation to the clause, laws are reviewed for their constitutionality using either strict, intermediate, or rational basis scrutiny. Strict scrutiny would mean that in order to distinguish based on a particular trait, the government has to have a compelling, narrowly tailored interest, and no less restrictive alternative available. Rational basis just means the government's interest is subject to a lower level of scrutiny (e.g. benefits exceed costs, or don't let in felons). Things like, race, religion, national origin, and some forms of alienage are suspect classes that merit strict scrutiny. This bit about alienage is important. As we'd expect from the above, when States enact alienage statutes, they're subject to strict scrutiny, and when those statues cross the line, the courts have found that State attempts to restrict resident or non-resident aliens encroach upon the federal government's exclusive control over entrance of aliens. Graham v. Department of Pub. Welfare, 403 U.S. 365 (1971). In other words, the federal government, not the States, decides whether various "aliens" are admitted. Note: State scrutiny levels when dealing with undocumented immigrants may be context specific. See, e.g. Plyler v. Doe, 457 U.S. 202 (1982) (children and education). The federal government's authority over immigration is further solidified by the Supremacy Clause of the U.S. Const. Article VI. See Mathews v. Diaz, 426 U.S. 67 (1967). As such, the courts have applied rational basis scrutiny to the federal government's immigration policy. One reason alienage is interesting is that it tends to encompass things like national origin and religion. This doesn't imply the federal government makes its decisions on the basis of religion. In fact, it'd be hard to make an argument that they do. However, since the categories can be so closely entwined, many scholars have argued for a change in standard. Edit In hindsight, this topic seems quite forward looking. A couple weeks after the OP's question a U.S. presidential candidate (Donald Trump) came out in favor of a ban on entry into the U.S. by Muslims. That led to a flurry of activity, and to this insightful blog post by Professor E. Posner.
The First Amendment generally prohibits the government from taking any actions to limit your speech, the same as adults. There are certain exceptions, particularly if you are enrolled in a public school, which has some latitude to impose speech restrictions to “avoid substantial interference with school discipline or the rights of others” Tinker v. Des Moines Independent Community School Dist., 393 U.S. 503, (1969). While you are a minor, though, your parents have virtually unlimited freedom to limit your freedom of speech. If they want to punish you for buying a hat or saying things they disagree with, they can generally do that. EDIT: The hat you've linked to probably would not fall within the Tinker exception. A similar case arose in Schoenecker v. Koopman, 349 F. Supp. 3d 745 (E.D. Wis. 2018), where a student was removed from class for wearing similar apparel supporting Second Amendment rights. The school made a vague allegation that his shirts were disruptive, but the court found that its concerns about disruptions were largely unreasonable and unsubstantiated. See also N.J. ex rel. Jacob v. Sonnabend, No. 20-C-227, (E.D. Wis. Nov. 6, 2020).
The First Amendment does not guarantee a right to not be offended. However, as held in West Virginia State Board of Education v. Barnette, 319 U.S. 624 (1943), it does prohibit compelled speech, and a person cannot be compelled to recite the pledge. The basis is not religion: this is a general prohibition on what the government can do. ("Parental consent" comes through the school informing parents of the right to not recite the pledge, and a parent who objects will tell their child to not recite the pledge, thus consent is implicit for those parents whose children do recite -- unless the child's actions don't reflect the parents' intent).