For the US, it's kinda interesting. It seems that when the original constitution was written, people kinda thought of the states as different countries. Robert E Lee seemed to think he had to fight for Virginia, for instance.

Nowadays, that thinking seems wrong. Not sure what yall think over there, but I've always thought of Michael Jackson an American artist, rather than a person from Indiana. I just don't see that Americans see the states as a federation of countries, but I guess people there might.

Something like the UN might have similar votes per country, on the rationale that countries are equal regardless of relative size.

Mass media and industrialization have definitely caused some convergence, but in the context of an America where it took more than a day for some intra-state trips this made sense. There's still definitely a lot of regional pride and some differences, most notably in Texas, which is rather unique in its mythology because it existed as a country for a short period and fought an independence war.

The US when it formed was probably more aligned with what the EU is today. That original setup was very impractical so they reformed into the current US with the Constitution in 1789.

For all practical purposes they were, or damn close to it. Modern conceptions of the nation-state are post-Napoleon, so when the Articles of Confederation and later the Constitution were put together, Union meant Union, however post-Civil War, that came to matter much much less.

There was an episode during the ratification debates where Rhode Island was almost left out of the United States. 12 other States had already ratified the new US Constitution but Rhode Island held out for more concessions until eventually it was decided that Rhode Island could ratify or leave the Union. Considering they were surrounded by much larger States who had prior grievances with Rhode Island, Rhode Island made the right call. Otherwise they’d likely be part of New York or Massachusetts right now.