I suspect the US would be like that. It won't be Civil War so much as a federal government that can't or won't protect us. Areas will defend themselves, with different cultures and different skill sets setting the direction.
Morgan Llewelyn is a wonderful writer of well researched and well thought out historical fiction One of her first books, The Winds of Hastings, though not as skilled as her later writing, brings alive the story of Elana of Saxony, one of her ancestors.
I ramble. My point is that it'll be another disconnected Dark Ages of sorts, but with some areas maintaining terrific survival skills.
I suspect the US would be like that. It won’t be Civil War so much as a federal government that can’t or won’t protect us. Areas will defend themselves, with different cultures and different skill sets setting the direction.