The nation will be lost as we lose our national identity and shared sense of endeavor. The impact of unbridled and less diverse immigration will be to change the entire country, not just the western states. We will take on the profile of a third world country with a large, permanent underclass and a wealthy elite living in walled compounds with private guards. This country will be taken down thru its own democratic institutions, i.e., thru the ballot box.
And will eventually be re-constituted (pun intended).
It appears that many tend to ignore the temporal nature of any generations' cultural orthodoxy (ie "political correctness" in its current parlance). 500 years ago, one could be burned at the stake for heresy; 225, tried for treason for challenging the throne; 100, persecuted for sexual "deviancy".
As populations are further segregated and opinions hardened, the power of current fashionable orthodoxies which give protection to anti-American rhetoric/policies will fade. Once the battle lines are drawn, who cares what the enemy thinks of you (or they you)?
At that point, innate human behavior, which has been percolating along & driving natural selection for 3-5m years, eg distrust of non-group members, lethal actions undertaken to mitigate/eliminate competition, etc will once again burst forth.
We won't be here to see it, but I am very sanguine about the eventual outcome for those future generations versed in the history of Western Civ who wish to enjoy the benefits of liberty for themselves.