Earlier quoted context omitted.
Why does that matter? There are huge differences culturally and socioeconomically between different states (and even areas). States have very different laws with a "federal government" managing it all. I don't see how it's very different from EU member states and the EU in Brussel managing it all.
There are a few ways it's very different. First is that the US has a national standard process for obtaining a passport that applies regardless of what state you're in. That is not the case for the EU. Second, not all EU member countries are parties to all the same treaties, again, unlike the US. Third, each EU country has its own domestic and international policy, restricted that may be as regards to international a…
Theres nothing stopping the US adding a state.