> A state is its population.

Oh that's not true at all. A state is an institution which is influenced by its population, but if anything, the attitudes of the population are more a product of the state, its constituent political parties, and the associated media apparatuses than of a freestanding "will of the people."

To give a trivial counterexample, if the American state "is" its population, then why does your presidential vote only matter if you live in a swing state, and why can you only vote for one of two candidates? Surely your vote should reflect all of your policy preferences and have equal influence no matter where you live.