You do not understanding the country and its people at all. Let's say DC gets annihilated with smuggled in nuclear weapons. Completely gone. Ok somebody in Nebraska is going to suddenly pick up up rifle and start shooting? At what? Is the Army (500,000 strong) going to enforce marshal law on the entire USA? No. Are the Governors going to assert their authority? Yes.
You people watch WAY to much TV and read way to many doomsday novels.
Read recent history.
The central power collapses, a lot of repressed grievances suddenly become bloody.
Do you really think that people will keep playing nice once the power of the FedGov is gone?