"And if the formation of a North American superstate would mean the abandonment of the Constitution?
Canada and Mexcio would never allow their governments to be dissolved and their provinces to become states of the Republic. Nor would they allow their sovereign countries to be considered only states.
"
Nonsense. Canada and Mexico would as easily do so as the USA would. However, an alliance does not mean a loss of sovereignty. My expectation is that the three countries will retain their political independence, but form economic alliances that include free travel and work for citizens of all three. That's not unconstitutional by any definition. Indeed, our Constitution has provisions for treaties of all sorts.
We are headed, unstoppably, I think, toward a EU-type of an alliance, with at least Canada and Mexico, and probably with more nations to the south. The stage has been slowly set for decades, now. I do not see any way it will not happen at some point, given the momentum already established.
I'm an old man of 60, but I expect to see this in my lifetime. It will be very interesting, to be sure. In my lifetime, I have seen enormous changes in the geo-political spectrum. Europe is a very different place than it was when I was born. Asia is even more different than it was. I expect North America to follow. It seems to be the direction things are going.
You want to fight this change. OK. Go for it. I'm just telling you that your battle will be a losing one. Momentum is on the other side.
As I said before, we shall see.