Who is there to attack Canada (besides the US itself)? The Great Britain is trying to return the lost colony? France is thinking about taking over the Quebec?
That's a bit more complicated don't you think? 70+ years with America as a superpower (20+ where it is almost the only one in its class) makes it easy to forget that things could have been massively different. Imagine a case where the Soviet Union did not dissolve, but stabilized as a military and economic equal to the US. Would you say that Canada's peace and prosperity would be guaranteed in this alternative universe? What about other countries in eastern Europe or the Middle East?
To give you an couple examples in the current real world, imagine if South Korea or Taiwan didn't have such good relations with America in the post-WW2 peace. It is not that far fetched to think that there could be a single communist Korea, Taiwan could have been swallowed up by mainland China.
I don't think that Canada in your alternative universe would've been worse off than Finland in this one. Finland's neutrality kept it safe ever since the WW2.
Swiss Neutrality did not save them in WW2 either, only German strategic calculus and the idea within the German high command that a mountain campaign would be too costly in military terms. It wasn't their neutrality that saved them, it was military deterrence. Push did NOT come to shove for them.
You cannot seriously assert that if Germany beats the UK and Russia, they will decide to simply leave Switzerland alone?
Protected from what? From the White Walkers?
Who is there to attack Canada (besides the US itself)? The Great Britain is trying to return the lost colony? France is thinking about taking over the Quebec?