The problem with your theory, pbrower, is that the GOP isn't extremist in the traditional sense, of being dictatorial and doing things people don't want. Half the country really, honestly supports the GOP and votes for them, which is why there cannot be a revolution against GOP policies. (A successful right-wing revolution in the US is probably more likely than a left-wing one, because generally speaking most rural areas (most of the physical territories) back the GOP and thus the Democrats could be easily defeated in a war in a series of sieges; not that a war will happen, but if alien space bats intervened and it did.) The map you posted below, in a good year for the GOP, is totally plausible. (If 2010 had been a presidential year, it might've been similar, though the Pacific Northwest should be D and Maine, maybe New Jersey R.)
...but is this a GOP year?
and you are probably right about any insurgency, but those seiges would be tough from rural areas...then again, biological weapons (rural people wouldn't have the infrastructure to deal with a large plague) would be the way to go as a Marxist and nuclear weapons would be the way to go as a White Randian Nationalist (Most Marxists would live in "one bomb territories").