So our CS graduates take the same courses, study the same material, and pass on the same grading scales as these international students from countries like China, India, etc that have come to attend American universities. Therefore it seems unlikely that they are categorically incompetent due to a flaw in their education, even if we make some allowance for them not studying as rigorously as their international peers for whatever reason.
However, if the news can be believed, we're now seeing a significant number of CS graduates who are unable to find employment. This is coming on the tail end of a bunch of highly publicized layoffs.
The notion that there "Aren't Americans to do these jobs" just doesn't track. I'm sure that there are lots of corporate executives who are saying that there aren't enough qualified Americans to do these jobs, but they're saying that because it's in their best economic interest to say that, not because it's actually true.