Divisions

 You have the original six figure division: The Northeast, the Feudal Core, the Gulf, the Plains, the Desert and Cascadia. (Quebec, Alaska, and Hawaii being outside the purview of the continental U.S.)

Cutting it into three, you would have the Forest Zone, the Grassland Zone, and the Desert Zone. Of course, the Gulf and the Pacific Northwest could be argued to exist outside the climactic designations, but as relatively narrow slivers of land, they could be said to still be part of their respective spheres of influence. The Gulf Coast would be a transition between Mainland America and the Caribbean, and "transition" means containing mutual elements of both cultures. Cascadia would see a lot of back and forth between the desert nations, and the District of Columbia is very much a Pacific Northwest society situated in the drier parts of the former Oregon territory.

You could say there's the division between the East and West, the delineation being the Mississippi river. You have the Non-Denominational sphere, and everything else. Eastern America is much more agricultural and populated. Western America , even when Christian, has become more esoteric, and is significantly less populated. Half of its population is composed nomadic herdsmen, and so even the settled communities (Which would probably very often be only a couple generations from nomadic hordes) would have values reminiscent of tribal societies. Once again, the Cascades would be an outlier on that front, but because of its distance it would still possibly have more in common with its nomadic neighbors than agricultural counterparts in the East.

East and West has recently seen the stark differences, in an East experiencing record precipitations, and the West experiencing droughts and unprecedented heat--even in the normally temperate Pacific Northwest.