Here is where the main problem - NATO.
Imagine (hypothetically) there is a preparation for Canada to ally with Russia what would you think US would do. Just allow Canada to give Canadian land for Russian troops and make America vulnerable? The world leaders need power, they are power hungry and your precedent is just a bait for them.
False equivalence. Canada was not subject to US occupation for decades or centuries prior to this hypothetical scenario, so it's unlikely to look for protection against a potential US military invasion the way Eastern Europe looks for protection against a potential (and now very real) Russian invasion.
But even if it was somehow a valid example, it would be wrong for the US to invade Canada in such circumstances and it is wrong for Russia to invade Ukraine. Two wrongs don't make a right and all that.
What harm these 144.1 million people did that they will face the consequences of the sanctions coming from all over the world?
And how many of those 144.1 million people are on the streets of Russian cities protesting against the aggression their government is committing against other nations?
Roughly zero, because protests are illegal and they get arrested as soon as they try to.