"Do the math."
It just depends on how much "civilians" are you allowed to kill, and with which weapons. And how long people armed with rifles stand before fleeing when all around them big bombs explodes and people die.
It doesn't look US had issues to occupy German and Japanese cities after having destroyed them, does it?
Look at how Russia kept Chechnya. Or how it crushed revolutions in Czechoslovakia and Hungary - when you can ignore the death tool, everything is far easier.
And the issue won't be a military coup - which would be quite unlikely - or Trump ordering to kill all Democrats, the issue could be a revolt of some "Tea Party" fanatics or some religious sect, or the like, which may not have at all the majority of the population on their side.