I came to post the same thing - sometimes Americans forget that they are a country of immigrants. And one of the routes for potential immigrants is college education.
But with a typically enterprising capitalist mindset, the American system also wants to ensure that talented individual don't go back to their country (or elsewhere) immediately after getting a degree. This is where the high cost of a US college degree comes into the picture - the burden of paying for it acts like an anchor for most students who come from developing countries or econonomically weak background. Even if they get some kind of scholarship and / or do part-time work, they still have to take a huge loans to live in the US to complete their education. And often the fastest way to repay these loans is to work in the US or other developed nations. This may take another few years. The American system hopes that by then the potential immigrant would be sufficiently exposed to the American culture and lifestyle and consider staying here.
(The high cost also ensures quality of education is high in the US, thus attracting talents from around the world. And the money is also pumped into a lot of R&D in the college allowing US to maintain a big tech lead. It's a neat system that seems to work so far.)
The other aspect of ensuring that higher education remains costly in the US is to also ensure that a blue-collar workforce continues to exist, and wage is suppressed among the white-collars. Perhaps the law makers also feel that it acts like an incentive to work more diligently, out of anxiety and worry - after all, people with more qualification, experience and higher stable income often tend to jump around more (which the big tech try to thwart by entering into illegal agreements to not hire each others employee).