The question is more are you irreplaceable - is there no way an American could do your job even if they may need more training?
We pay taxes, we compete for limited schools and jobs, yet far more people want to come here than leave. Americans have become a lot less wealthy the last 40 years relatively thanks to stagnant wages and skyrocketing prices.
The last thing we need is an unlimited supply of competition that only moves in one direction. Average H1B salary is like 60k, rich companies like MS are employing thousands of IT workers. These are jobs that anyone here could do with a 1-2 year online technical degree.