nation state 
noun
A sovereign state of which most of the citizens or subjects are united also by factors which define a nation, such as language or common descent: Nepal emerged as a nation state in the eighteenth century...
- The reliance on national governments and the nation state leaves the door open for the most reactionary forces.
- Like neighbouring Mali to her west, Niger is not a nation state defined by one language and one race, but a Commonwealth of peoples.
- The sovereign nation state, so the argument goes, leaves little social policy role for the European level.