> Personally, I have directly encountered this shift. I was advised by professors and career advisors against pursuing a Ph.D. because, I was told, I would face disproportionate competition from foreign students, making it an uphill battle. When applying for jobs, I have been explicitly informed that my race and gender alone could be a barrier, not because of my skills or work ethic, but because of the current political and hiring climate.

I think you are lumping together two completely separate things in a way that doesn't make sense: 1) policies to try to encourage hiring of women/minorities and 2) the fact that Americans often don't have what it takes to compete with much stronger foreign grad students (isn't this in fact meritocracy)