Expect and prepare for the worst, anything that turns out better will be a pleasant surprise.
They do shoot paper citizens oversees though. Granted, paper citizens aren't actually Americans, but there's no legal distinction or distinction that most people consciously recognize.
IMO military/police types always seem to think it'd be much cleaner cut than civil wars have been since the ACW. That'd there'd be bright flashing signs saying Civil War time, that Biden would come out and give the emperor Palpatine speech from ROTS or something, and then they'd have a few months before they got their orders to mull it over and coordinate with each other.
Nah, you'd be getting told stuff like "national emergency," that you need to restore law and order so that we can just resolve things peacefully, that you're just needed to federalize the national guard, that you're only providing logistical support to the national guard, that they're only fighting White Nationalist and National Socialist terrorists and criminals which are being supported (or even actually are) by Russia and China.