Another Kingdom? How is it that San Marino could survive as a sort of democratic society for a thousand years while the only other area to have something close to it is run by academians from the American Northwest? Whenever I read of this universe these days I think of the title of an Onion Article. Which one? In Retrospect, I Guess We Might Have Resorted To Cannibalism A Bit Early
Actually, most of the post-Change states are, in fact, democracies (you can have hereditary leaders in a democracy, if they enjoy popular support). The MacKenzies are literally a town-hall meeting style democracy. Corvallis is Athenian-style democracy, with (Athenian-style) oligarchic tendencies. It's not our modern style of democracy (with Robert's Rules, and a head of state who is regularly replaced), designed for governing republics of millions of citizens, but it
is democracy.
The ones that aren't are literally top-down (i.e. someone imposed that format, rather than the masses choosing it for themselves) autocracies of one form or another. The PPA is an in-your-face aristocratic "republic" (the Barons functioning as something of a Senate, in practice, since they are collectively too important for the Lord Protector to simply rule by fiat in the face of their displeasure). Iowa and the "Square States" are initially civil-military juntas (pretending to be US States operating under "Emergency Powers"), and develop into mild autocracies (dropping the fig leaf of still being democratic Pre-Change states, once the new generations grew up).
Rather than "kingdoms" (though that word is used), most post-Change states are basically the organic outgrowth of strongman(strongwoman)-centered survivor clusters. With consequences for how they are governed. "Ted kept us alive through the Change Years, so it's unlikely we'll be kicking him to the curb to make way for parliamentary democracy (especially since Ted controls the military, most of the food supply, and everyone in the government is personally connected to Ted)".
The only "I don't really buy that..." moment regarding democracy is that Signe managed to voodoo her way into making the Bearkillers a hereditary monarchy, in the face of Havel's public desire to see it become an elective republic with an elected Bear Lord (and a House of Commons). Even if people were inclined that way (and remember, they fawned on every word out of Havel's mouth, so it's unlikely), they'd have picked Will or Eric (the 2nd and 3rd in command of the Outfit, respectively)....not an infant with two older sisters*.
*-we never do get a real glimpse of why Ritva and Mary bailed on the Outfit to go live with Astrid...other than Signe had "become impossible to live with". There's a lot of room for darkness in that, given the favor Signe shows to Mike Jr (she might have tried to use the Twins as matrimonial currency for support from important A-Listers for Mike Jr).