That's correct. The U.S. has always been a favorite destination for the brightest minds from all over the world to come work in its universities and research labs.
But since 9/11, increased scrutiny and hightened visa restrictions have stopped the best and the brightest from entering the United States' talent pool. The following is an excellent article written by Robert Gates, the President of Texas A&M University and former FBI boss in the NY Times where he talks about the challenges faced by the U.S. in maintaining its edge in scientific research: Robert Gates' article in NYTimes
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But since 9/11, increased scrutiny and hightened visa restrictions have stopped the best and the brightest from entering the United States' talent pool. The following is an excellent article written by Robert Gates, the President of Texas A&M University and former FBI boss in the NY Times where he talks about the challenges faced by the U.S. in maintaining its edge in scientific research: Robert Gates' article in NYTimes