Because too many immigrants have reduced Americans earning power to the point where labor is too plentiful and, despite the current propaganda, current wages are too low. When I was growing up 1 earner could raise a family, have vacations, cars etc. No 2 breadwinners can't. Too much immigration turns us into "them" and not "them" into us.
Kaslin you can go black to wherever you came from anytime. Virtue signalling immigrants that come here now want to flood us with "your kind" so you don't feel like a hypocrite. I get it. PS: Immigrants don't do the native population any favors, we just put up with because the political power to stop is suppressed. NOBODY WANTS TO BE INVADED.