While this would be desirable, I see it as difficult, given the USA's reluctance to accept even the modest provisions of NAFTA with just its contiguous neighbours.

I think the belief in its self-sufficiency, and the chronic inability to play nicely with others, would make the USA a reluctant member of any closer union, and probably a domineering one if it came about.

But as you say, the geopolitical tectonic plates are shifting - we shall see where they end up.