A country, nation, or nation-state was a governing entity that was generally smaller than a planetary government, and made up of smaller subnational entities, states, or provinces, as was found in many instances on Earth.
The United Federation of Planets required that planets have a unified government in order to be considered for Federation membership. However, planetary citizens often felt an attachment to their native region, which may have previously been a nation-state. (TNG: "Attached")