Toronto and southern Ontario is definitely Great Lakes and would be part of any balkanized Great Lakes Commune. Northern Ontario is just too different. The St Lawrence plus its watershed is its own thing too, maybe Maine or northern bits of Vermont could in it but it's different from New Engalnd and Acadia.

Maritimes would obviously envelop Newfoundlound but would resist New England. New Brunswick MAYBE might be part of Quebec remnants or St Lawrebce Watershed. Northern Quebec would split off the St Lawrence watershed.

There already is a thing in northern Alberta and BC called the Peace Region and it was a thing all the way back before the settlers came. Southern Alberta, Saskatchewan, Manitoba would probably be in some confederacy depending on if Alberta could chill enough. Southern BC obviously just aligns with Cascadia.