One thing I find implausible (the irritating kind of implausible, since it's basically being pushed into the narrative/World for no real reason) is that the entirety of North America east of the Mississippi and south of Maine is, at best, small towns and villages or backwoods family-tribes. IOW, no significant civilizations.
Ah...here's how this works:
There are basically two* types of survivor clusters in the immediate post-Change world.
You have the McKenzie/Bearkiller/Corvallis type, where a coherent group makes it through the first Winter, with the necessary spread of skills to maintain a fairly high material culture. They then expand outward and absorb/hegemonize smaller or less well-off clusters. Barring disaster, they level out at a 1900's (without steam or electricity, of course) material culture (even if their military is phalangites and horse archers). By CY 30 or so, the only real limit on their expansion is peer neighbors or their birthrate.
OR
You have the Southsiders/Brushwood/Boy Scout type, where something went wrong (or they just got unlucky) and the group who survived 1998 lacked the skillset or toolset or something to retrench at a sustainable level of technology above Neo-Bronze Age.
IOW, it's really a choice between Victorian City-State (or Ranch-State, as the case may be) or Hunter-Gatherer. Barring freak accident (read: the exception), there really isn't any in-between option.
If a small community of any real size (a few hundred to a few thousand) survives 1998, by the time CY 23 rolls around, it should be at least as big and dynamic as the McKenzies or the Bearkillers.
Ergo, the East Coast (from North Carolina down to mid Georgia or so) should be pockmarked with pocket kingdoms at least equivalent to the McKenzies or the Sun Valley Buddhist Collective (or whatever they are calling themselves). Not just "small towns" (by implication much, much worse off than the Norrheimers) and hill clans.
Also, Stirling keeps referring to the "East Coast Megalopolis".....which is sort of (intentionally, on his part) misleading. Yes, there is a bona fide Megalopolis on the East Coast, but the East Coast is not a Megalopolis. The Megalopolis exists, but it's primarily in the Northeast, stretching down to northern Virginia.
Several of the South Atlantic States are extremely rural, once you are out of the few major cities. West Virginia, North and South Carolina, and parts of Georgia have many small population centers that are effectively unapproachable by refugee plumes** (which, as a very reliable rule, follow the roads and the gradient) and have natural geographic barriers between them and the cities. Agriculture (especially what remains of the US' subsistence agriculture) is widespread in those states.
Florida is screwed, though.
*-entities like the PPA are statistical outliers, since their behavior is markedly different (their expansive phase essentially kicks off immediately).
**-we've talked about this before, but it needs to be spelled out. You cannot simply draw a 150-200 mile radius around an urban area and say "refugee swarms hit everything in here, ergo Death Zone". That's not how it works, ever. Refugees follow the (main) road and the gradient (i.e. refugees almost always go downhill, absent people chasing them). They don't leave the road unless they get chased off of it (and then they attempt to get back on the road ASAP). Therefor, people fleeing the urban areas will form a "plume" that has a geometry controlled by geography, the major roads, and their endurance. Not a radial "blast zone".
Some small community 50km outside Atlanta or Aberdeen or Munich might never see a single refugee from the City, because a line of low hills/forest with no primary road (Highway/Interstate/Dual Carriageway) is shielding it. OTOH, columns of refugees moving down the Interstate or the M6 might go 100+ miles (more, if on bicycles) before they succumb to attrition.
And that makes sense. In Europe, anyway, I'd say things will be different with the Japan thread (on an unrelated subject, Rising Sun had issues but I enjoyed it overall and it was really cool seeing how the spectre of Grantville is hanging over everything, even the far side of the world).
