Although the project is named "Medieval America", Canada often finds itself folded into the scope. It's easy to see why; Most of the country's population is found at the southern borders, closer to their American counterparts than each other. Since a country Canada's size, with such displaced population, and in rather inhospitable conditions, could probably not maintain itself politically, we see the various provinces absorbed into the culture of their Southern neighbors. Ontario becomes more of a Midwest kingdom, Vancouver is one of the Cascadian city states, the Maritimes are assimilated into the Yankee naval empires, and Alberta is pastureland for the cowboys. But then there is Quebec.
In modern times, Quebec has managed to remain culturally distinct. It is a province of several million people who have managed to carve out a society that speaks French on a continent that is otherwise rooted in English or Spanish. It has also felt more European than the rest of North America. It's a true quirk in the modern world. In Medieval America, it would be interesting to see what kind of identity it has taken on, especially since the linguistic world would be just as different as anything else.
The language would probably be very fluid and gradually changing from one region to another. There is the common ancestry, so from coast to coast it would probably owe itself to English. Dialects and colloquialisms would then splinter as we passed the Mason Dixon line, the Appalachians, the Great Plains, and the Rockies. These would be the barriers in which the tongues stop being as intelligible with one another. The south would also see be kissed by Spanish, with maybe even Creole working its way into the Gulf Coast. We may see more Amerind influence out in the western, isolated spots. (Give a thousand years, and the West Coast could morph into something else entirely) But what of Quebec?
French could possibly have worked itself into the language of as little as one million people, or as many as five million. The first thing to keep in mind is, if any language is intact in these nine-hundred years, it's Quebecois French. To the people in these province, nothing defines them and their way of life as much as their language. It could potentially be preserved as if it were Latin. The cold and relative isolation could certainly help in preserving it. But I do wonder if it would be satisfied being its own enclave. It doesn't have the best piece of real estate. Also, remember that Quebec prides itself on how different it is. Give the desperation of long winters, and a generally warlike medieval society, and it doesn't take long for "different" to transform into "better". I can imagine a cultural tide of conquest coming for and retreating over the centuries. This has probably affected New Brunswick and eastern Ontario, which take bi-lingualism more seriously than the rest of Canada. It has also led me to wonder about New York.
I found it funny White created a page for New York, but did not include its flag in the Northeast or Feudal Core maps. Culturally, New York can resemble the Mid-Atlantic, Midwest, or even New England in some places. (Though New York City is part of the USA empire) There could be several reasons for this. One is that maybe it's just very unique, or mostly important as a trade stop. (White has another orphaned flag around Virgina) It may not be included as part of the Northeast because it is both feudal, and occupied by knights. (The Northeast nations are either republics, or mostly infantry) Maybe it's too inland to be part of the Northeast. But it did occur to me that maybe at one point, it was conquered by Quebec. It would be a decent prize. Better farmland, and access to the Hudson river would certainly make it the gateway between the Midwest and Atlantic. (Quebec has always lamented the Eerie canal and its "bypassing" the St. Lawrence River) It would make sense too, with the Statue of Liberty as its flag. Both a very New York (And Non-Denominational) icon, but also one that lends itself to France.
If Quebec is an empire, it's a vestigial one, maps indicate. But whatever its current state, I believe just as the Anglo-Saxons had a large effect on Mainland Europe, the Quebecois have had a mark on Northern America.