The West Coast, cut off from the central government in the east...
Wait what? How the hell does a single ash cloud cut half the country off from the other half? Especially in this era of airplanes, satellites, and Internet?
And while I'm at it, if this is bigger than Krakatoa, how was only the Midwest affected? That kinda of crap should be causing a worldwide Year (minimum) Without a Summer.
...and several million died from starvation and exposure over the following months.
Where does exposure enter into this?
War broke out swiftly and unexpectedly.
Really? Wow, they must suck at expecting war.
Texas broke apart...
Seems like that would be the state likeliest to stick together.
Since then, a series of new governments have claimed control over different portions the former territory of the US...
Kinda surprised no one else tried to seize bits of the US. Mexico and Canada, if no one else.
And North Korea, but they wouldn't succeed. Because they're a tiny country that no one likes.
The center of the country, from Kansas to Ohio, has changed hands many times, and has been reduced to an infertile warzone...
How? Unless people started nuking the most fertile land in the US, there's no way that would happen--and if they did, it would still bounce back. The fact that Chernobyl isn't visited by humans more than balances out remaining radiation, which is higher than the aftermath of an atomic bomb because pretty much all the fissile material in the bomb...fizzes? immediately, leaving relatively little long-term radiation. Point is, unless they salted and glassed the Midwest it should still be fertile.
Sorry. You just seemed trying so hard to take yourself seriously. I'll read the rules and get back to you.