There is the other side plenty of workers successful at programming language could be trained to fill any gap. That's what happened in the 50s and 60s..
PS The number of roles that there aren't qualified Americans for could be counted on one hand. This has always been about reducing salaries, not shortages.
Of course I am exaggerating, but this is not a 1 dimensional problem.
This is why in the modern world some sectors are always crying about "worker shortages" while asking always more migrant workers to come in - salaries are compressed as a result, and locals have no incentives to enter the branch.
Hence importing workers may be useful for needs that are limited in time and space (say, install a specialized foreign machinery in a power plant), but systematic importation leads to dequalification of the local workers, who flee the branch that has now low salaries.