That assumes only nation-state-level entities. This has been a very poor assumption: even within my lifetime, the last ~40 years, we've seen nations like Yugoslavia and the USSR break up, and some of the successor states (eg. Slovenia, Croatia, Ukraine, and the Baltic States) have developed robust democracies where previously totalitarian communist governments existed.

Within the territory of the U.S, states like California and NY and Massachusetts continue to have robust democracies even if the federal government doesn't. In California's case it's often a bit too robust, and we often get ourselves into trouble with ballot propositions that have a lot of popular support even when they're economically unworkable.