I think when SHTF you will sure as hell see some impostors.
raid jackets can be found online, and any douche with a gun and a navy blue button-up shirt and matching pants can pose as one.
same goes for military most people think “he is wearing camo and has a rifle, he must be in the military”
don’t be fooled and don’t cooperate (not saying resort to violence first thing) even if they turn out to be genuine.
(because in USA the military will most likely send you to a FEMA camp)
it will help to understand and recognize what kind of uniforms are used by your military (by that I mean the camoflage patterns)
for example the military here used to use the M81 camouflage but don’t any more, that said you can find them at virtually and surplus store for $5
so if I see a guy calming to a part of the military can could use ammo to help out his unit, I wouldn’t trust him