A full scholarship to somebody that decides to move back to their country because of racism and xenophobia still directly benefits the US if that research was done here. The smartest students in the world passing on the US does not help the US. With more policies like this the smartest students in the US might move to other countries so they can work with a larger pool.
Don’t forget that America’s technological heyday—when Silicon Valley was built in the first place—came during and shortly after the Johnson Reed era of immigration restriction. Companies like Apple, Intel, etc., were founded between 1960-1980 (the decade on each side of when the foreign born population hit the historical low in 1970).
Your comments often lack evidence of these poor neglected Americans.
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Responses like yours really make me think that the bottom line for many people is doing whatever benefits foreigners.
It's called brain drain, and doing the rest of the world the favor of putting on the brakes is something that would be quite far out on the spectrum you'd call "woke" if it was done for the reasons one would arrive at when really thinking it through (which clearly has not happened)
Americans would throw a fit and say it was a grave threat to American technological superiority, national security, etc.
It's obviously good for a country when it can attract the top talent from around the world.