The U.S. education system will stop teaching basic civics or the 3 'R's in favor of Maoist retraining, non-Socialists will fight each other harder than they fight the Leftists seeking to destroy the nation, and the U.S. will elect a racist rabidly anti-American/Western Communist to the highest office of the land and allow him to turn the federal bureaucracy like the IRS and DOJ into a personal Praetorian Guard.
Oh wait ...
Timing light....sheeeit. I haven't used one of those since the early 90's.
Don't forget to add a couple extra degrees of advance for the altitude.
Non human race extincts us?
Seriously, focus on the "likely" events, not the unlikely made-for-tv stuff.