Timber isn't the only thing in Canada, actually, there is a vast amount of oil and even some uranium. I question how much uranium they used up though, even if it was a huge commodity it still has a long life even huge nuclear power plants don't use that MUCH uranium to my knowledge.
I'm aware of the oil deposits in Alberta and elsewhere, but I think they'd have been gone by 2076/77, given the Fallout setting.
Don't remember exactly, but I think Alaska and the Poseidon Oil Rig were the last two sources of oil in the world.