1/ Training goes all the way down the pipeline to colleges. If x% of students are foreign, then Americans didn't have the opportunity to get the education.

Again... the skill issue falls apart when you consider teams at tech companies having 1 non-American national origin or caste. I'm very skeptical that, between two foreign candidates with the same U.S. education and experience but different national origins, the fact that the candidate whose nationality matches the current team composition is selected can be explained purely as a matter of skill.

2/ Great, lets train up more American engineers to push the demand higher.