Can't find a list on the wiki (maybe i'm just dumb) but off the top of my head:

America, duh. Forming conditions are pretty complicated but basically, if you're americanist, conquer the south, if you're evangelical, conquer the North.

Nouvelle France. Be Louisiana, conquer 150 places.

Zion. Be Mormon, control greter Zion region, which is Deseret, Socal and parts of Jefferson and Idaho.

If you're playing as California and expand to the north or past the rockies, you can form the northern and eastern protectorate kingdoms.

other than that every culture can form a titular cultural empire if they hold 150 holdings (yes, every culture, even the super obscure offmap ones)

in terms of kingdoms, if you're Catholic and hold the three Tennessee duchies you can form the Kingdum of Tennessee and you can also form the Kingdom of west Virginia if you hold the corresponding territtory.

if you're Deitsch (pennsylvanian Dutch) and Anabaptist and hold the Kingdom of Dietscherei and the one west of it you can from the kingdom of Pennsylvania.

not really formable, since it's de Jure, but often missed. but if you somehow manage to control Bermuda and the Equinox Islands (off the coast of california) you can form the Empire of the Seven Seas.

If you control it's historical Territory, you can form Gran Colombia.

New Mexico is also a titular Kingdom that can be formed if you control the Duchy + any other Duchy. New Jersey is similar if you hold the duchies corresponding to it's territory. Also very similarly, in New England you get the titular Kingdoms of Maine and Mount Vernon.

Oh yeah, the Kingdom of New York (Gotham) can also form "The Empire State" by decision, allthough i never really saw the advantage over the De Jure atlantica tbh.

There's probably more, but that's all i can think of right now.

correction: not every single Culture has a culturel empire, but most do, including the Offmap ones.

Thanks my dude you're a savior. Cheers mate...