I think you covered the answers well there KB. There may be another reason though. Foreign student levels in America have dropped drastically in the last few years. I would say that this co-incides with Americas foreign policy, which is in my opinion, seen as far more aggressive than it has been before. It has certainly alienated a lot of people around the globe. Bush's policies have made the world less safe, not more, and this makes people more nervous in their dealings with it.
The other maybe just 'retaliation'. It is harder and harder to get a work permit, or any visa, for America nowadays. Natural reaction for countries must be to do unto others as has been done unto you.
I think Americans are getting off lightly.