I know in the 90's the military asked their people if they would fire on U.S. Citizens in a civil war, and something like 70-75% said no. Its the only reason this has been drawn out so long.
Every army soldier and marine I know have a distaste for our government, and the way things are run. There is a reason the terms BOHICA and FUBAR came to be.
Short of using tactical nukes to hit major cities, the government wont do as well as people have an illusion they will. The best defense is to make yourself seem more powerful than you are. Half the things the government would have to do to stop a civil war would get them too much negative publicity. They cant risk having NATO countries turn on em.
I mean, it will be brother having to shoot his own brother, brother and sister killing each other, parents and children....not gona happen, the military will step down faster than the government would be able to compensate for. Of course they will use desperation tactics, and their inset networks. But still...the chance of success for a nationwide war is higher than people think. Each state will either become a rebel state or a loyalist state. Military bases would likely change hands, or at risk of being so be destroyed. Even if the government won, it would be through a peace agreement.