Your source on that? All the schools I’m in contact with are still as international as ever in their CS PhD departments. I’m not sure what the trends are outside of CS, but I can’t imagine they would be very different. I think you are just pulling this number out of thin air.
Research is funded quite differently from undergrad programs. Sure, fewer TAships are available, but your research funding is much more detached. DARPA and NSF aren’t going to become stingy all of a sudden.
> Regarding the "racism against Americans," there is no such race, and if there were one it would not explain research productivity.
If I claimed (without any evidence in fact) that “Indians or Chinese are less productive than Americans” I would totally be accused of racism even though both India and China are multi-ethnic. It is especially a stupid thing to say as foreign and domestic students are pretty diverse, with slackers (or dreamers) and very focused students on both sides.