I have 5 suggestions for Canadian PODs
(1) Had Great Britain fallen to Germany in either world war, I think it quite probable that the British government and fleet would have moved en masse to Canada a la the Portuguese government to Brazil in 1807.
Such a move would have greatly enhanced Canada's involvement in world affairs, making her the de facto, if not the de jure, head of the worldwide British Empire.
I can see all sorts of conflict between Canadian national independence and loyalty to the British Empire. How would a Lloyd George or a Winston Churchill act or be received by local Canadian authorities?
How would an isolationist United States react? It would be one thing for neighboring Canada to send her troops far overseas to fight for the British Empire but quite another for Canada to be the headquarters of an Empire fighting a world war which would bring that war to North America.
For starters, German U-boats could concentrate in large numbers off the North American coast actively going after the Canadian havens of the British fleet, rather than being hemmed in by a blockade thousands of miles away at the British Isles.
Bringing a world war so close to the shores of North America would be of great concern to the United States and this could definitely affect Canada.
(2) Oregon: If 54' 40" came to a fight between Great Britain and the United States in the 1840s could be an interesting POD, especially if the entire Oregon Territory was absorbed into Canada.
(3) If Alaska was bought from Russia by the British and became a part of Canada in 1867
(4) If the British had seized Louisiana from Napoleon before he sold it to the United States as the Louisiana Purchase and it became part of Canada in 1803.
(5) The state of Vermont was actually independent of the United States during most of the 1780s and early 1790s and flirted with rejoining the British Empire. Supposing Vermont had become a part of Canada instead of a U.S. state in 1792, I can see lots of complications for U.S./Canadian relations in ensuing years.