The fact you're downvoted to grey saddens me. For heaven's sake this is a tech forum and especially us techies should very well know that immigration and open exchange of people and ideas is the key to success.
Because people are tired of identity politics being shoved down their throats, not because they're against immigration per se. The fact of someone's race or origin is far less interesting than the story of these individuals, their personalities, their minds. If race or origin comes into it, it's if it plays into these deeper stories. But we don't want people telling us that they should be "pointed out and repeated". It's both irksome and facile.
I don't think open exchange of people is useful, or ever has been. What has helped the U.S.'s "success" (in kicking ass, generally speaking) is one-way brain-draining of other countries.
There are many people in science who go to the US for research for a couple of years and then go back home - and people from the US going abroad to escape uncertain funding, enjoy new perspectives (CERN!) or the myriad of other issues that the US has (healthcare, discrimination, public schools, transportation).
Edit: I would upvote parent comment as well as grandparent.
Edit: I think it would be fair to this at some kind of ratio (e.g. spend 10 karma to for each upvote or something).