I've noticed a couple of immersion problems. The demographic spread isn't proportionate to reality. Looking at social sciences and human history, we know that even people of the same culture, but separate racial background are not going to work together. Especially in a time so dark age esque, brutal, tribal and so forth. I live in Quebec and I can tell you outside of Montreal there is very few people who are not French Canadian. The province itself is 88% French Canadian and almost entirely homogenous. The only area with people of other cultures is the island of Montreal, and the aboriginal reserves just South of the island. Canada in general has significantly less African American people who reside in it. Make Vodun their religion, or a newurban culture themed religion where Lil B (Who refers to himself as, and is referred to as Based God) is their god.
When you finally get the West coast going, you should make the Vancouver area, and perhaps enclaves of the west coast US ruled by Asian rulers and perhaps an Asian-American culture. Maybe a new Neo-Confucian religion, as this is what realistically would happen in a cataclysm. People of different cultures, and especially backgrounds are not going to magically band together. I suggest turning Florida and the Detroit area as the designated de-jure lands of African American characters, as the city of Detroit is 83% African American, and Florida is slightly less.
The peninsula piece of land where Toronto is located should also be primarily Asian, and secondarily Indian. I'm sure we can use the Indian portraits for this. If any European characters are in Ontario, they'd be likely in the rest of Ontario. I also wouldn't make Southern Ontario one kingdom at start. Maybe two duchies, with the Toronto area being a duchy, and maybe the Ottawa area being a small kingdom or vice versa. To add some spice to see who unifies Ontario. But making the Toronto area's culture Asian American, and isolated from their far Western kin on the west coast.
I've also noticed that most of the Western European portraits resemble that of Mediterranean peoples in CkII without the Mediterranean DLC packs. In other words, everybody has dark hair and light eyes, which is definitely not accurate. Especially in the Northeastern US, the Martimes and Ontario-Quebec. Quebec especially being settled by Breton and Normans colonists. Later, an influx of Irish and Scottish. Quebecers are either very fair featured, or very pale with dark brown eyes and hair.
Sorry for the long reply, I just figured you'd like to hear some opinions. This is one of my all time, favourite mods alongside the Winter King and I just want to help as much as I can with immersion and realism.

