sure, but there's the obvious counterfactual: if those engineers were scarcer, that level would likely be paid more

But it wouldn't result in more domestic workers being hired. Those companies would just have smaller workforces in the US and larger ones abroad.

Big Tech has hired functionally every domestic worker interested in and capable of doing the job. They pay so much already.

Correct!

Employers benefit from regulations that exist to benefit employers. We should have completely open borders or actually do what's best for citizen workers.

Employers would have to pay more competitive wages if the candidate pool was smaller. Then there is the free legal services given to some workers and not others, that leaves less budget overall for compensation.