America has never been a champion of immigration, and honestly I don't really remember a time that the 'floodgates were open' so to speak, and it's not even a partisan issue. The last major immigration tightening was Bill Clinton with IIRAIRA in 1996 while the last amnesty was Reagan in 1986.
Don't take my word for it, here's what Benjamin Franklin, founding father, had to say.
"Those who come hither are generally of the most ignorant Stupid Sort of their own Nation, and as Ignorance is often attended with Credulity when Knavery would mislead it, and with Suspicion when Honesty would set it right; and as few of the English understand the German Language, and so cannot address them either from the Press or Pulpit, ’tis almost impossible to remove any prejudices they once entertain." - Benjamin Franklin, 1753.
Tell me that's not a highfalutin 1700s take on "they're not sending their best, folks."
> We could onshore factories and staff them from all over the world.
That doesn't need people, it needs robots. The factories of the future have zero people inside.