Europeans think of any European country as an equivalent to America as a whole.
Half of the problem with that phrase is that this line of thought is far more common from Americans than Europeans. No European think France = US in any other context than geopolitically, maybe. But a lot of US citizens do think that way. The phrase “Americans think 200 years is a long time, and Europeans think 200km is a long distance” is of US origin. It's literally the result of US ignorance that compares the geographical distances of a single European state, like Germany or France, to the entire extent of the continental US. Europeans are perfectly aware that 200km are 200km anywhere on the planet. Whether you are driving to another country or another state, it is irrelevant.
The other half of the problem is that the political dynamics of the European Union are fundamentally different to the United States federation. Just by the fact that the US was forged in war while the EU is an economics first agreement. Their nature is vastly different and not comparable at all. Maybe one day in the future the EU will just be a federation of states, a single country with a single constitution, but today that's not the case. There's no executive power in the EU that can override a country's authority. That alone sets them so very far apart.