I don’t know how other armed forces work, but we probably had someone on our Submarine from at least 40 different states. Everyone is rotated to other boats or shore facilities every 3-5 years. Officers rotate 2-3 years. There is so much crew turnover that it would be impossible for an entire crew to support the Captain- they just aren’t together long enough. Not like hundreds of years ago when armies tended to be loyal to their commander and followed blindly.
My point is thus- if the Captain told us that California is in open revolt, or terrorists have taken over LA, etc- do you think that the dozen or so Californians on the boat would go along with a strike on civilians? I sure as hell would not want my submarine to send tomahawks on South Carolina right now - knowing my wife and kid are here. I wouldn’t want them to fire on Dallas, TX because my parents are there. I have family in Washington, DC too.
There is also free press here- with varying degrees of liberal/conservative bias, but they are there. I don’t think the public could be duped into thinking the state of California are all terrorists if they were defending themselves from the US Army.
If there was a Civil War, all branches of the government would split. You have congressmen from different states; Supreme court justices from different states; a president from another country ( :-D… ok Hawaii). Every military unit would have to decide which side they are on.
A handgun can still kill a man, even wearing body armor; so yes the ‘farmer’ with a shotgun could fight in a civil war; perhaps not against a tank battalion, but in the streets, in his home, etc.