Hispanic illegals can at least be deported, which is a legal/political 'out' to stem the tide; I don't know how to even begin reversing H1B's followed by chain migration.

Watch Canada closely. The US's larger population has a proportionally longer incubation time, but Canada's is a similar illness & endgame. I suspect that heritage Canadians will be in the same boat as South African whites shortly, but with a chinese/indian majority vs. a bantu one. Triangulating between SA now and Canada in two or three decades should give a decent bead on what the US can expect if its demographic shift continues.