superstate

/ˈsupərˌsteɪt/
noun
  1. A large and powerful state or political entity formed by the union of several smaller states or nations.
    • The ancient empire was a superstate that controlled trade across the continent.
    • Some people worry that the European Union could become a superstate that overrides national laws.
    • In the science fiction novel, a global superstate governs all of Earth.