> To even get to this point you would have to assume that the US would devolve into a civil war, in which you can also safely assume that many in the US military would be defectors (leaving a lot of empty tanks and airplanes, if not turned to the "other" side).

This is totally speculation on my part, but it could be important to have a armed civilian resistance to create a "permission structure" for military defection. My understanding is that military strongly inculcates loyalty and obedience to the organization. Those seem like they'd be hard feelings to overcome, especially in isolation when the defection would be solitary and likely pointless. I'd think that in a lot of cases people would just muddle along for lack of options. Having a group to join and take your equipment to seems like it would make the decision much easier.