Annexation and becoming US president Imagine I was born in country X at xxxx. At xxxx+20 years country X is annexed to the United States. (Freely or forcefully) At xxxx+40 years I am elected to be the next president of the United States. Can I legally be elected?
At the time of annexation of country X someone would have to decide the status of the countries citizens: If all citizens of X are now citizens of the USA, and whether they are legally citizens from the date of annexation or since they were citizens of X, and if they are considered residents in the USA since the day they became residents of X, and if they are retrospectively "born in the USA" if they were born in X. And other things, like whether non-citizen legal residents of X are now non-citizen legal residents of the USA. That has to be decided for many reasons, and the answer to your question follows naturally from this. Maybe you could check on a history site if anyone knows how this worked with Hawaii.
Why has this never been interpreted by SCOTUS? It has never been interpreted by any court, because the interpretation you're advocating is nonsensical, and nobody has ever tried to advance it in any court. Therefore, no court has had an opportunity to rule on it. Congress, however, has (at least implicitly) interpreted this clause to mean that all natural-born citizens are eligible to be president if they also fulfill the other requirements, regardless of when they were born, so that is the prevailing interpretation unless someone manages to challenge the interpretation either before congress or in a court. If such a challenge is made then there will be an explicit ruling.
There are two models for citizenship, by location of birth and by the nationality of the parent. The US chiefly follows the first model, which is why only your grandma's father is American, and your grandma is not. By the same logic, you are not. Countries like Spain are far more lenient, and do allow you to request Spanish citizenship if you can show any of your direct ancestors are Spanish. That's possible because each country can make its own laws within reason. The international norm is that everybody should get at least a citizenship at birth; statelessness should not happen.
I was initially going to vote to close this as a political rather than a legal question, however, I think there is scope for separating out the two dimensions. Our society makes a distinction between children and adults by giving them different legal rights, obligations and protections. If you think about it, there are a lot of things beyond sexual activity where the law does this: voting, drinking, military service, compulsory schooling, legal culpability etc. What things are subject to legal restriction is a political distinction. Now, there is no reason politically why these laws could not have been drafted to say "children can do this, adults can do that" and leave it to the courts to decide who is a "child" and who is an "adult". Biologically and emotionally people reach maturity at different ages so this is perfectly sensible. It might even be more just. However, justice is only one thing that we require of our legal system. Among the others are certainty and efficiency. Providing a bright line based on birth date gives certainty. Not requiring the court to deal with this on a case-by-case basis increases efficiency - justice is not free. This is why jurisdictions use age as a proxy for adulthood. As to why they choose any particular age, that is a political question.
Nobody so far has discussed Electoral law e.g. Representation of the People Act 1983 There are various clauses that may be relevant, one of which is: A voter shall be guilty of bribery if before or during an election he directly or indirectly by himself or by any other person on his behalf receives, agrees, or contracts for any money, gift, loan or valuable consideration, office, place or employment for himself or for any other person for voting or agreeing to vote or for refraining or agreeing to refrain from voting. Subsection 2 similarly makes it an offence to offer employment to induce any voter to vote or refrain from voting but somewhat less concisely. I believe this would make such a contract unenforceable.
At least one such person was naturalized, according to Wikipedia, in 1868, a time at which I believe naturalization was conferred by district court judges. Although this doesn't perhaps constitute a court case, as asked by the question, it does show that formerly enslaved people who has been born outside the United States were not automatically granted US citizenship. Wikipedia says: Although native-born American former slaves became citizens upon the passage of the Fourteenth Amendment to the United States Constitution in July 1868, this change in status did not apply to the members of the Clotilda group, who were foreign-born. Cudjo Kazoola Lewis became a naturalized American citizen on October 24, 1868. The passage cites Dreams of Africa in Alabama: The Slave Ship Clotilda and the Story of the Last Africans Brought to America by Sylviane A. Diouf
What could be the consequences of this wedding? They would be married For example, if they break up and end their PACS in France, would they still be officially married in the USA? Yes, and also in France. And if after that they marry other partners, could this be a problem for them when applying for an American visa? Yes, bigamy is illegal in both the USA and France. Does France and the USA exchange information on wedding of foreign citizens on their soil? Don't know, probably not. Could they even end up being officially married in France even without doing any paperwork themselves? Most definitely. France recognises US marriages so they would be married in France (and the U.K., and Australia, and Germany, and ...). This is true even if the French government doesn't know they are married.
Can I choose to not register my child as a US citizen? No. Your child will be a US citizen regardless of whether you register anything, and (unless you have spent less than 5 years in the US, or less than 2 years after you turned 14) regardless of the place of birth, because (in that case) even if the child is born outside the US he or she will be a US citizen under 8 USC 1401(g). Can I register them with an 18yoa deadline for them to choose citizenship? No. Your child probably (depending on your wife's citizenship, and assuming birth in the US) will be a dual citizen from birth without the need or the ability to choose. On turning 18, the child will be able to renounce either citizenship, but will not be required to renounce US citizenship and will probably not be required to renounce the other citizenship either. (I am not familiar with all EU countries' citizenship laws, so the law of that country might have a requirement to choose, but there is no such requirement in the countries whose laws I am familiar with. If the other country is the Netherlands, the child will risk losing Dutch citizenship on turning 28 unless he or she takes steps to avoid that or unless the law changes.) As pointed out in a comment on Putvi's answer, if you successfully avoid letting the US know about your child's birth, you would be in the awkward position of needing to get a visa for the child if you ever want the child to leave and reenter the country. Otherwise, the child would be an illegal alien in the eyes of the US (this assumes you've managed to hide the child's place of birth). There is no process available to get visas in the US for (non-diplomatic) children born in the US, of course, because such children are citizens of the US.