Do we really have enough native STEM workers in the US?

Yes, actually we do. Too many.
Turns out that little law of supply and demand does in fact hold true. The higher the demand for something in limited supply, the higher the price (wages) you will pay for it.
By applying forces to this law, you impact a number of outcomes. That is, if you start monkeying around with the supply, sure, you can adjust the price you pay for the STEM. And, you get a whole host of other, well, I’ll call them unintended outcomes, by doing so.