Damn, Sam Stone beat me to Strange Brew! It is of course the definitive Canadian film
Seriously, if you like Denys Arcand, you should check out Robert Lepage. He is one of my favourites. Some of his best are Le confessional (takes place in Quebec City during the filming of the Alfred Hitchcock film The Confessional), Nô (flips back and forth between Expo 1970 in Japan and the October Crisis in Quebec) and my current favourite La face cachée de la lune (about twin brothers, both played by RL, opposite in temperament coping with the death of their mother and the disappointments in their lives - very full of fascinating imagery). Interestingly enough, Robert Lepage played the part of René in Jésus de Montréal (the actor who wanted to do the monologue from Hamlet).
I also second the Atom Egoyan recommendation, especially The Sweet Hereafter, about a schoolbus crash in a small BC town. (I have a soft spot for this one, since it was filmed in the area near where I live).
For some Aboriginal perspectives, check out Atanarjuat : The Fast Runner (Inuit) and Dance Me Outside (Natives in Ontario).
Also, Margaret’s Museum, which takes place in Nova Scotia, is a slow-moving, but very well-done film about a mining town in the 50s. This one stars Helena Bonham-Carter.
Why Shoot the Teacher, starring Bud Cort (from Harold and Maude), is the story of a teacher who arrives in a small town in Saskatchewan during the depression.
I don’t know how many of these are readily available in the US, but they are IMHO all worth the effort.