Okay but comparing it to the whole EU is nonsense especially when you compare its “diversity” to only spain and find it wanting comparing the examples you gave to Catalonia vs Basque county vs Galicia and you can find similar major differences in many individual EU countries. The US is not a monolith no but compared to a multiple country alliance is insane.
Okay but the confederation of states has one of the strongest centralization in the world so pretending the US is some bastion of local autonomy is nonsense.