Well, without picking at any of the numbers and what they actually represent, the real key here is awareness that when crap comes down, all bets and predictions go away very quickly.
There is just no way of knowing how a lot of people would react and then act on either side until it actually happens.
How much of the US military strength is currently occupied outside the US? How much of that could be brought home on short notice? And without igniting a huge mess in multiple parts of the globe with the power vacuum created by withdrawing?
The US military has never had to deal with guerilla warfare of the potential scale here. No one really has. Uncharted territory. The sheer magnitude of the geography of this country is very daunting when you start talking about subduing a rebellious population.
How much of a military force was required to control the few large urban areas of Iraq? Something like 1/2 million? Nowhere near the scale of the US and its major urban areas.
I am old enough to remember the Detroit riots of the late 60’s; I was in Michigan at the time. That was a type of geurilla action, but it was eventually put down by a combination of National Guard and LE efforts. Detroit was small potatoes as warfare goes, but it was really messy.
I figure if it ever came down to it, we would not only be up against a very well armed and organized state/federal force, but also in the mix would be a heck of a lot of armed Rats/commies, especially in urban areas. In a way, I envision something like present day Syria or Lebanon in the 80’s. So it would be a combination of revolution/CWII rolled into one big mess. I pray to God this never happens.
With a leftist government, if it came to shooting it out with the citizenry the effort would be to get as much of the military as possible offshore as quickly as possible. Leftists NEVER trust the institutional military and always maintain it just to repel foreign attack or prevent it. They fear it at home. They always move to purge the officer corps. Carter did it. Clinton did it. Hussein is still working on that. Got to flush out all the experienced officers and NCOs to be replaced with Reliables. Even the military is not trusted and will not be used against the population unless the paramilitaries that leftists in power always build cannot handle the opposition. The military will be filled with a parallel officer corps whose job is to keep the active commanders in line or kill them if they get out of line. Much of Hussein’s continuing desultory warfare is designed to keep much of the military out of the country. Even the Soviets did not trust their military and it did betray the commies in the end.