The River Kingdoms are detailed in full at http://pathfinder.wikia.com/wiki/River_Kingdoms
There are some differences in this world, however.
Major River Kingdoms are:
Pitax- A land of bad culture, offensive art, terrible music and frightening poetry. Your neighbor.
Mivon- Sharp traders' land. Currently Ruled by "The Lady." (Snooki). She came to power after the Merchants' Council deposed King Pauli. Pauli currently sits again on the council, hoping again for another turn at rulership. The Lady believes very much in expansion and development. She is particularly interested in acquiring more Shoreline since the more rivers a Kingdom has, the more trade that can be done.
Daggermark- Known for its spies and its poisoners. Not to be trusted. Daggermark controls other countries through influence rather than through directly absorbing them. It has several principalities basically under its thumb paying tribute. Its most hated enemy-state is Mivon.
The Grand Lord Matro Lindovar rules here, elected by an oligarchy for life or 20 years.
If he dies, and a female takes over, then her title will be "The Grand Lady"
Protectorate of the Black Marquis - Pirates in the River Kingdom seas.
Great Easterbrook - Land of mining and hardcore jousting. Known for its heavy cavalry.
Lina - Rivals to Easterbrook.
Napier - Rivals to Easterbrook.
Outsea - Founded by Ceratodi and Boggards and Sahaugin. Often embroiled in war with Oppara and Rellik. Friendly relations with Pitax.
Razimir - Ruled by a God-Emperor who is Sardax's brother. Razimir has poor relations with its neighbors who are concerned that the God-Emperor may seek to expand. The country was previously three small city-states that Razimir united.
Rellik - Land of proud knights and small fifedoms. Rellik is locked in a long struggle with Outsea, Daggermark, and Mivon for territory, being in a cold war with 1 country often while he fights the other two. Rellik is always at war with the "freaks' in Outsea. The city also lives in fear of Razimir.