I know a bunch of folks who are certified A&P mechanics. They work hard and sometimes really ridiculous hours ( split shifts, rotating shifts within 7 days, etc). Since airplane safety depends on their qualifications I want the very best ( kind of like my choice in surgeons).
I do not want some third rate, non-English speaking, foreigner coming here to take those jobs ( and yeah lots of folks who were laid off have not been called back because of these foreign workers).
This has happened in nursing as well. So many of the RN positions have been filled with heavily accented and heavily recruited Phillipinos that some hospitals in California are darned hard to understand anything anyone says.
And by the by try handling some of those airplane tires for an evening then tell me about where your sympathy lies (you are probably a desk jockey somewhere)
I have no doubt it's hard work. But it seems there are plenty of people willing to do it, so I value it at whatever the market pays for it.
I am indeed sitting at a desk, but the market seems to value what I do (which sometimes involves working for 80 hours a week) more highly, even if you dismiss me as a "desk jockey."
And there's no guarantee that immigrants will be inferior to American workers. The random illegal you hire off the street is probably not particularly qualified, but I've talked to businessmen who find too many American workers--particularly union workers--lazy and entitled, and immigrants generally much harder workers.