em·pire
n.
1. a)A political unit having an extensive territory or comprising a number of territories or nations and ruled by a single supreme authority.
b)The territory included in such a unit.
2. An extensive enterprise under a unified authority: a publishing empire.
3. Imperial or imperialistic sovereignty, domination, or control: “There is a growing sense that the course of empire is shifting toward the... Asians” (James Traub)
... So yes, it could be considered an empire.