If the federal government disappears tomorrow, each state has a National Guard that would be sworn to obey the Governor. No state level leaders would take kindly to armed thugs running around.
The main reason the Republican establishment tolerates their fascist wing is because ditching them means losing every election to the Democrats. Moment the two-party deadlock is broken nationally and each region has a clear majority party, the desperately needed political realignment would begin and most local politics would becomes less bitter.
Anyone advocating violence on any side would be stifled. It's the closenss of elections that gives the crazies power.