There's also State Guard / State Defense Forces, which are solely under state jurisdiction. But in many states, and especially in blue states, it has devolved into a uniformed and militarized but unarmed organization.

However, this entire line of thought presupposes that those people (whether in NG or SDF) would align themselves with the state and against the feds, and that's not given at all. I know from personal experience of close interaction with my local right-wing militias in WA state that quite a few members are in NG or WSG.

The same goes for armed populace. It's true that there's a lot of weaponry in private hands, and we're not just talking your stereotypical AR-15, but stuff like say .50 BMG anti-materiel rifles, grenade launchers, and even privately owned tanks and artillery in some cases. However, they are disproportionally in hands of people who lean far right, so in event of open conflict I would expect them to work with the feds. There are some of us on the left who are heavily armed precisely so as to counterbalance that, but we are outnumbered by an order of magnitude. Then there's the issue of training - right-wing militias actually get together and train, and while it is derided as LARPing - often for good reasons - it's still better than nothing. More importantly, it's not just training but also networking - those people know each other and have plans to get together and coordinate "when it's time".

Indeed, a particularly nasty possibility is that Trump wouldn't even need to issue any kinds of explicit orders to federal troops, but rather just let the right wing paramilitaries loose by simply not doing anything to stop them (and making it widely known that there will be no consequences).