That's true for post-graduate students. Some of the numbers get kind of fuzzy for several reasons: undergraduate statistics sometimes not included, some students entered with permanent-resident visas, some are continuing post-graduate study under fellowship agreements, etc. Many do have temporary working visas because companies recruit them aggressively.
Foreign students in the US are declining about 20% a year anyway since there is a confused policy. Corporate and academic America want them for their skills and tuition, some politicians want to exclude them as an election issue, but American students are not hindered by foreign students.
Interestingly enough, the US isn't even near the top in percentage of foreign students in tertiary education. It ranks 17th in OECD countries.
In international mathematics assessment of 15 year-olds, the US ranks tied for 21st among OECD countries.
In problem solving for 15 year-olds, the US ranks 23rd.
I'm not a fan of teacher bashing. It's up to the parents to motivate their children to pick up a book on their own, learn the content of a course and develop good study habits. If their child isn't learning something, then pick up the book and help them with it.
Americans kids still only do about an hour per night of homework. That isn't something teachers can control.
