It is an interesting point as to whether our LEGAL immigration policies drain other countries of their best and brightest talent.
I see another slant to this....
The fact that we import the best and brightest has the side effect of masking the fact that we are not producing the best and brightest from our own schools.
Yes, we do have the best universities in the world - that's why foreign students come here. And this is precisely my point. Our K-12 system is not producing enough talent to fill our universities and the demands of an economy that needs a constant flow of brains.
It's no accident that if you go into a hospital the doctors are probably from another country. Our mathematicians are all too often born elsewhere. Ditto all too many of our engineers, physicists, nurses and other professionals.
I am not making an xenophobic comment here - please don't misunderstand. I am trying to point out our inability to produce these people from kindergarten up. There is a disconnect between our K-12 system and our university system. This flaw is masked by talented immigrants.
We don't realize we can't product enough doctors to fill our needs - because we import them. This masks the problem of our own school system.
Immigrants have always augmented our natural talent even when our schools were better than they are now. As I recall Einstein was an immigrant.
In other words, we are not taking responsibility for our future needs, but relying on third world countries to pick up the slack for us.