I didn't read all the responses because I'm at work and trying to handle 6 things at once.
Anyway, spending $600 billion a year on the defense budget makes little sense when we don't invest in the future of that military budget. We sell military technology. However, we do not sell our current, best, most badass military technology. We sell the meh stuff. If our country continues on the path it's on, with education costs continuing to skyrocket, we are going to lose our edge. We won't be selling meh stuff we will be buying it.
The government will generate more revenue this way because these individuals will generally be higher income earners. Also, they'll be able to contribute more to the economy once they graduate. I have a $1600 student loan payment (I'm not in STEM so I'm not arguing this for me). That's $1600 a month I can't use to stimulate the economy. I graduated with ~300 kids and about half have as much student loans as I. That's $240,000 a month not being pumped into the economy. From one school. For ten years.
I wouldn't make it retroactive, though. And if you drop out before completing your degree, you'd have to pay that back. Granted, not at the current, highly inflated, everyone can go to college because the government funds student loans.
IMO, no one goes into STEM because they've been fed propaganda. They go into political science, philosophy, art history, or some other meaningless degree.
I agree with trade schools. Generally speaking, a trade school is significantly cheaper than a 4-year degree, which is why they weren't a focal point.
I would rather spend $18B on education and bettering the future generations instead of a wall that's not going to solve the alleged issue.