There are a few more points that could be added.
But it boils down to, it would SUCK for everyone.
War sucks.
Civil War even more so.
There'd be spies.
Traitors.
Units getting tired of killing citizens turning on other "loyalists" soldiers.
Starvation.
Electrical outages.
Military Units are used to having secure supply chains. All of a sudden, everything they need is difficult to get.
Bases need to be run. Many civies help the military run those bases. Now which ones can you trust?
It goes on and on.
It all adds up to "It SUCKS".
True. But it probably wouldn't be a civil war very long. At least one of the bad boy countries, russia, china, iran, etc. would probably start taking a pot shots. Then other countries would pick sides and then the dumocraps would have started the third sucky war. Not much would survive.