The fall of the Roman Empire is the best analogy to our situation imho....there was no real Civil War (though some colonies did rebel and there were some slave rebellions)...eventually folks moved away from the cities and started evading taxes...and when .gov ran out of money to pay the soldiers the soldiers fled as well.
I think one of the major things about the fall of the Roman Empire was the the money situation, the leaders started stealing more of the money, wasting more of the money, and had no desire to even try to balance the budget, kind of sounds like the Democrat party and the RINO's, I think if the USA is to fall in the near future it will be similar with the money situation, as things get out of hand.