The error you are making is assuming that we need any foreign workers at all.
We don’t. Full stop. We could kick out every foreigner and require full citizenship for every job and be perfectly fine - not only that it would be a massive benefit to the vast majority of Americans who earn a living by labor.
The mistake you are making is assuming there are always citizens available who are qualified to do the job AND are willing to work for wages the employer can afford. STEM college is hard and many Americans do not wish to go through a curriculum such as structural engineering which has the highest flunking rate.
yep