I have zero real world understanding of the skilled immigration debate happening so I asked brother in law who works at a major tech firm:

He describes a similar problem to the Under represented minorities in medicine problem. 

By the time you’re applying to firms like his, majority of applications are from Asians.. 70-30. There just aren’t that many Americans applying. 

This firm has multiple interview stages - live coding problem sets, etc... and full time hires are paid the same regardless of immigration status. 

He noted there could be an issue with over-reliance on contractors that skew towards h1b’s.. but I asked him if a solid American candidate would have an issue getting hired.  

His quick answer : Absolutely not. Lots of jobs. No idea why more Americans aren’t choosing these areas given how good the pay is.