There's also a plethora of people with CS degrees who can't even write FizzBuzz on their own, even given a warmed-up IDE and a partially filled out skeleton of the program. And no, this is not idle speculation, I've interviewed quite a few of these people. So I wouldn't personally put much stock in "has a CS degree" as a marker of qualification for any particular job. That applies, of course, regardless of nationality.
Having worked with a lot of foreign tech workers - I’d take the Americans any day.
Having worked with many Americans and many non-Americans over the last 35+ years, I'd say there's no general difference in ability that correlates to nationality. I've worked with dumb Americans and dumb non-Americans, and vice-versa.
Where are all these people? Every time I post a job, I get thousands of garbage resumes.
The H1B program today acts to undercut American workers.