@debtinflation was making a pragmatic argument: that modernity renders these granular state lines obsolete. My point is that the EU manages to keep chugging with all these little sovereign states of 5-10 million people managing their own healthcare and retirement systems

Maybe a US state is something legally different than an EU country, maybe not. I would say the two weren’t intended to be different, and whatever trends have produced such a difference were a mistake. Either way, that doesn’t address the practicality question.

Look at the specific examples I provided. European countries closely coordinate their regulation of radio spectrum, air traffic control, nuclear power, and pollution through the EC even if individual countries have separate national regulators on paper.

Sure. Obviously the US does stuff. But that’s very limited compared to what happens (and people want to happen) at the federal level US.