Presumably, it will cost less for them to make it than it will for Americans.
I'm still trying to understand how that's bad for America.
Is this based on some kind of outlook where jobs are a scarce resource that are an end unto itself, and if somebody else does more work that leaves less work to be done by us, and we then suffer for the lack of work for us to do?
I gather you would have been a signer of Bastiat's candlemakers' petition too?
http://bastiat.org/en/petition.html
Edit: Let's say it was like you just said though. Suppose "the Mexicans" were just going to give us F-250s. Since you put it that way, do I infer correctly that you would agree that that would make America better off, and not worse off if they did that? Because if you concede that, then your entire case in the OP of saying this is somehow putting America last is defeated.