I hear what you’re saying. What boring people to be afraid of novel cultures.

Anyway, fine, close the border and make it so only US citizens can do all the labor nobody wants to do. Watch how much doesn’t get done; the economics behind work and such don’t change rapidly. I’ll bet most small farmers get destroyed with fields full of rotten cross because nobody can offer a citizen enough to do the work that still yields a profit. The billionaires with factory farms and prison labor will win out.