I have no idea how many US service members there are in the US but it’s a non issue for two reasons. One, the US population far outnumbers them and two, I bet when the fighting starts there would be a lot of desertions because it would mean killing their friends, family and fellow countrymen.

Pessimistic defeatist attitude won’t get us anywhere.

Edit: oh and before I became a socialist my friend who is in the military (and has been for a while) reminded me how effective guerrilla warfare is. See: Vietnam and Korea.