In 2026, even though the U.S.
had 50 member-states and the E.U. had only 27 states, both unions were large
enough to constitute what in historical terms, with the European early-modern
rather than (the smaller) medieval kingdoms in mind, empire-scale republics. As
long as elected representatives hold office at the federal level in both political
unions, both unions can be said to be republics (as well as containing
republics—or, as Ken Wheare wrote in Federal Government, “wheels within
a larger wheel”). Were either union to have only five or so states, the empire
definition would not be satisfied. Also, that definition includes the requirement
of cultural heterogeneity between (as distinct from within) the states. Being
on the same (empire) scale is just one of several ways in which the two unions
belong to the same political type. It was in this respect rather than based on
the sheer number of states that Sophie Wilmes, vice-president of the European
Parliament, said that the U.S. should not regard the E.U. as a little sister
(i.e., a junior partner). I contend that she was correct.
The full essay is at "The E.U. and U.S."