I think a major issue is the lack of a feedback loop. Cheap money in america means that no matter what country you're currently in, it's financially beneficial to migrate to the US. One of the happy paths towards this end is migrating for college or higher education.

In other countries' colleges without this unlimited input second to local students, there is a feedback loop connecting the college back to the local schools. This ensures that schools keep up. In america this is not required, since no matter what standard say UW sets, the corresponding tutoring centres in India, China and Singapore will adapt to that within weeks. And they can send as many students as UW can possibly ever want.

It also doesn't help that international students bring in more money than local students.