His basic point is correct. For a variety of reasons, this country produces fewer scientists, engineers, mathematicians than it needs. The immigrants we import in these fields do an incredible amount of heavy and important lifting. In industry and in academia where they train the next generation.
My own department (economics and finance, the closest things to technical fields in business and the social sciences) has been greatly enriched by colleagues from China (3), Indonesia, South Korea, Jamaica and Ecuador. Plus a couple others who are children of immigrants.
We are conducting a job search for a tenure-track position to teach finance. I'm having dinner with the first of three candidates tonight. She from China by way of LSU. Very impressive job paper. Very personable. Good teaching evaluations. If there were more Americans like that we would hire them. And there is one American-born candidate among our three finalists. But they are few and far in the more technical fields.