The *interesting* question is whether the European NATO countries will respond when Canada has to invoke article 5 when the Americans invade for a third time,

LOL.
Would that be about the quickest invasion in recorded history? Over by lunchtime?

You seem to be gloating about the prospect, which I find disgusting.
Practically speaking you may be right, because I think it's not beyond the current American regime to pull a Hiroshima-Nagsaki on Canada. - Dropping a couple of modest nukes on a couple of small towns in Canada, after which the Canadian government will inevitably choose to surrender.

One that I read recently opined that what will shake out when things settle down will be the that world will resolve into 3 general spheres of influence headed by Russia, USA, and China.

If you look at the size of these countries, in terms of population and economy, the notion of three spheres is ludicrous. Russia's population is 9th in the world, behind Pakistan, Nigeria, and Bangladesh. Its GDP ranks 11th, behind Italy, Brazil, and Canada. Russia is no more than a tail being wagged by the Chinese dog. China has long nurtured countries like North Korea and Russia as surrogates in its patient campaign to undermine the world dominance of America and its allies.

But regardless, if that is some version of real politic, it is mind boggling that any patriotic American would accept it lying down.

Elan