The disintegration of eastern Canada is one of the more fascinating topics in political history due to its modernity, its 'velvet divorce,' relatively non violent nature, and the fact that it probably happened due to a singular event,
Joey Smallwood coming down with severe trichinosis in 1946, on the eve of the Newfoundland National Conventions. Smallwood was a force unto himself, but without his leadership and advocacy his side lost the debate over whether to join Canada or remain an independent dominion of the UK 45%-55%.
It's always funny how there are so many WW2 TL's, or POD's of the Truman / Zhukov detente of the late 40's, or of a united China under either Mao or Chiang, but most everyone ignores the fact that Quebec was a part of Canada as recently as 1967 and that New Brunswick and Nova Scotia - PEI just recently marked their 10th anniversary as US states.
But lets say Smallwood doesn't come down with trichinosis and is able to persuade Newfies to join Canada rather than go down the inevitable path to US statehood, does that make a difference in the Quebec separatist movement? Or even if Quebec still separates, is Canada's national identity and GDP strong enough to rescue the Maritimes from the collapse of the cod fishery in 1995 and keep them from looking to Newfoundland - Labrador for guidance, which had insulated itself thanks to its 50 year relationship with the military?