My only complaint about the map is that you seem to not be in line with official national boundaries in USEA. Erusea is much larger, with both Delarus and Amber cutting into its territory. In fact, Delarus should be in a completely different place. That being said, I think this map is more official than the actual "official" map will ever be. Good job.
Pretty awesome. So Osea is sort of a US-equivalent, and Usea is....? It includes both Korean-sounding city of Baekje, British Oxford and French Acquitaine...sort of like a more ethnically varied EU? Yuktobania - Russia perhaps? Verusa=China? Emerria is Italy? And I have no idea what to make of the fruit salad of nations between USEA and OSEA: fascinating details, to say the least.
The game's developers did a really careless job with some of the worldbuilding, so the placement of cultures makes no sense at all. The way I BS it away is:
Western and Central European cultures originated on Anea (the continent with Emmeria) and Europa. The Oseans fled the Christianization of the Anean Empire in the 400s, initially landing at Colcastra. When Europa was taken over by Muslims in the first millennium, many Christians fled to Anea, causing severe overpopulation. The Papacy funded exploration overseas, leading to settlement of Usea and the eastern and southern parts of the Osean continent to alleviate Anea's overpopulation.
The Osean continent was populated by indigenous people based on Native Americans. The Oseans formed an alliance with an Iroquois-like confederacy between the Bannion Sea and Oured Bay to fight Plains tribes on the peninsula extending westward. The confederation still has some autonomy, but the Plains tribes were enslaved for the next two centuries. Indigenous people in East Osea didn't fare much better, but there's an independent country that they still control, FATO.
Usea's a hue melting pot from Muslim, Asian, and European settlement. They generally haven't gotten along too well. Also it got hit with an asteroid in 1999.
Here's some fanon stuff about the bigger players and important events: