In his book, Fed Up! Governor Rick Perry of Texas provides a basis for viewing the states of the U.S. as equivalent to the E.U.’s member-states. All of these states are semi-sovereign, as they have all transferred some governmental sovereignty to federal institutions. This implies that the E.U. and U.S. are commensurate. I contend that both are instances of empire-level and scale federal systems in which the federal level is both international and national in nature. This distinguishes both unions from international organizations on the one hand, and the state governments on the other.
The full essay is at "American and European Federalism."