Like Cascadia, there is no subregional map that depicts Quebec. This makes sense, in that it's still Medieval America, but it's still not hard to talk about Canada in the scope of this project. Most of the country's population is found at the southern borders, closer to their American counterparts than each other. In the event of a societal breakdown, the idea of a "Canadian" nationality may wither--at the very least they would likely share the habits of their southern counterparts--when they're not outright conquered. Ontario becomes more of a Midwest kingdom, Vancouver is one of the Pacific city states, the Maritimes are assimilated into the Yankee naval empires, and Alberta is pastureland for the cowboys. But then there is Quebec.
Quebec is most well-known for being a unique, French-speaking concentration of people (with the population of an average U.S. state) on a continent that speaks mostly English or Spanish, the especially the former as far as proximity is concerned. It definitely definitely beats to its own drum in the way nowhere in America or Canada does, and remains independent-minded, to the point of radical separatists in its history. The world of Medieval America gives such iconoclasts their wish, with little outside forces in a position to tell it what to do.
The east map does not show the entirety of Medieval Quebec's political borders, but this map shows that some kind of organized knights-and-lords government is fairly extensive in the former province, only fading away once we reach the near uninhabitable northern reaches. (The U.S. is also said to have territory in the Gulf of St Lawrence, but fairly small.)
Because Quebec is one of the oldest settlements on the continent, and maintained fairly old practices until relatively recently, it's fairly easy to picture as an "older" version of itself. The seigneur system was the longest-lasting feudal-like government on the continent, and the Catholic Church maintained a grip on the province until the the Quiet Revolution of the 1950's. In general, Medieval Quebec is probably not appreciably different from colonial Quebec, or Medieval Europe.
The biggest challenge, would be language. As mentioned, Quebec goes to great lengths to preserve its heritage as a francophone sub-nation, which is fairly easy with mass media and the written word, but languages in a pre-Industrial society are quite mutable. All across Medieval America, slang ("soda" vs "pop"), dialects (Think the Boston accent vs the Southern accent), and the proximity to non-English speaking communities, to say nothing of the way language naturally diverges, has created wide, variety of spoken languages. Quebec French is even quite different from European French. However, it's probably better preserved than most languages on the continent due a couple of things. First, because most of the population will be consolidated along the St. Lawrence. Secondly, the Church only has to maintain its authority over a million or so people, allowing the written word to be pretty uniform. As a result, the Quebec court probably has the most intact of the ancient tongue.
You'll notice on the map I created (I certainly anticipated the Quebec flag better's than I did for Cascadia) , there's another flag for New York. This is because, as the New York state flag is on neither the Feudal Core or Northeast sub-region map, I speculated that that at one point upstate New York has been conquered by the Quebecois, but this language map doesn't seem to indicate there was a major cultural impression one way or the other. Still, if Northeastern New York was in some way franciphied, it would be fitting, as the Statue of Liberty was originally French creation. It should also be said that the trade map seems to show the area as a producer of wine, which Quebec, with its Catholic sacraments, European traditionalism, but rather cold weather, would certainly be a market for the libation, so perhaps we should call a map that includes New York and Quebec "Winter Wine Country".