system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5 what is student debt and why is it such a big thing in the US

I'm a french redditor and everybody mentions this thing called student debt in some subreddits. I tried googling it, I got no clear explanation.
gpt
In the past, if you went to college in the US, you were pretty much promised an above-average job with a decent salary. There was also a strong stigma against manual labor jobs (mainly because they become far worse as your body ages) and a lot of praise for office jobs for how much money you could make in some fields.

In the 90's, the generation that grew up on these ideals had kids and wanted them all to go to college. All of them. So suddenly massive amounts of kids were being pushed into college. 

The colleges reacted by raising their prices. Sometimes this was justified: they had many more students so they needed more dorms, more food, more teachers. But ultimately, college prices went out of control. 

The parents still wanted to send their kids to college (thinking it was how they'd get a good job still) and decided to take out loans to pay for their school.

BUT these loans were taken out on behalf of the kids so the loans were in their kid's names (in most cases anyway).

All at once, a lot of kids with college degrees flooded the job market. Employers now had millions of applicants with college degrees. In the past, they'd have many applicants but one or two would be college educated. Now...everyone had one.

This meant that the college degrees lost a lot of value. Since everyone had one, it stopped being special. There *are* plenty of degrees that are still useful and that you needed in your field (medical, legal, financial, computer science), but a lot of kids (myself included) were told that they'd be fine no matter what degree they got. And many were misguided by the college system (who wanted money more than for their student's to be well-prepared for the ever-changing job market).

And of course, it's super easy to argue that a teenager, with no real world experience, shouldn't be making a decision that will cost them tens of thousands of dollars, that will also greatly impact the course their career.

So now...we've got a lot of kids with degrees that may or may not be useful. They can't get a job in the field they studied for. Well, they can still get low paying jobs in another field just to make ends met. No big deal right?

WRONG! Remember those loans? That doesn't go anywhere. These young adults suddenly have a lot of debt to pay off. 

If their degree/career didn't pan out, debt. 

If they have a great job and make decent money, debt. 

If they have a medical degree and become a doctor and start their own private practice and make great money, debt (the average US doctor pays their loans off after 10 years).

We now have a huge generation of young people saddled with massive debt with no way to get rid of it and few ways to improve their circumstances. There's no real way they can afford bigger investments like a house/condo since they're constantly paying towards debt. A missed payment does horrible things to your credit score, a lack of disposable income screws up your livelihood and social/romantic life, and without skills to get a job that can pay the debt off the debt just gets worse. Best case scenario is that the debt takes years and years to pay off with no missed payments and it's still a massive source of stress in a person's life.