Earlier quoted context omitted.
Doesn't that potentially raise the salaries of all non-American engineers who might get jobs?
Yes, at the expense of American engineering salaries. Not a bad thing for innovation/technology as a whole but does lower American salaries.
You would not have this immigration issue (issue as in companies trying to get larger quotas and less restrictive conditions) if you would have enough competent engineers in the US. The problem is that companies HAVE to look outside of the country to find capable work-force. It's also worth nothing that one of the prerequisites of getting an approval of a H1B visa is the fact that you can prove that the position you are trying to fill cannot be (at least easily) be filled with finding someone locally. You also need to show (and guarantee) that the person whom you are hiring on the visa, will get paid higher than average salary for the same position in that field. So essentially there are mechanisms in place to avoid companies bringing in pointless cheap labor - how those rules are enforced is up to the government tbh.
It is also worth nothing that the "crusade" against current H1B laws also include some other, very important points, like getting rid of the silly H4 visa that H1B holders spouses are forced on.
All in all I suggest digging a little more into the issue instead of commenting from a very shallow point of view.