If the link above is accurate, the proposal for a more unified Europe after Brexit (EU2?), would focus on security, the migrant crisis and econonomic cooperation. Given the Russian invasion of the Ukraine, the refugee situation and the exit of Britian from the econonic co-op, these all seem to me logical things to be concerned about.
On the other hand, the notion of a 'superstate', with entirely merged armies and economic systems, and the elimination of national borders, is the opinion of one official in Poland.
But in the headline, the two are merged as one fact. Such is the state of journalism today.
But to your point, I'm wondering what the impetus would ever be for the U.S. to even remotely consider such a move. There is no external threat, military or economic, that would be better handled by an association of north/central American nations, as opposed to us going it alone. And the idea of fully opening our borders seems like a political non-starter, doesn't it? In any case, it has no attraction for me.
I'll just add that I"ve been talking to a lot of liberals about a lot of things for a lot of decades, and I've never once heard this idea proposed. But at the same time, I'm not in my 20's anymore, and there could well be a sentiment brewing there that has entirely escaped me.