Sure dude, EU and US, same principle, same as united nations, united airlines and IUPAC. Same principle, they are a union of things, if you mean that as "principle", sure.
EU doesn't have rules that everyone has to follow, they have agreements, that are often very specific between nations. UK was part of the EU with their own currency for example. So no, it's not the same type of union, unless you simplfiy it to "union of things"which of course is the same principle.
Also any member of the EU can leave unilaterally (like the UK), not so much for the US. I don't think they follow the same principle, again, unless you think of it just as a "union of things"
EU definatly have rules everyone has to follow. They're often called "directives" and are not optional. E.g. the 2021 ban on single use plastic cuttlery.
That was decided by EU. Members then have to implement it and reach that goal within a certain timeframe.
EU also decide what can and can't be imported into EU.
True, but my point is that if a country decides not to follow one of the directives, they can just leave if they want, they are agreements that they want to be part of, they are not merely imposed by EU. Nothing like the US and their federal government.
This is like saying that marriage and a double match of tennis are the same type of union or follow the same principle, no, they are not.