I'm going by the Wikipedia definition, to wit: "An imperial political structure can be established and maintained in two ways: (i) as a territorial empire of direct conquest and control with force or (ii) as a coercive, hegemonic empire of indirect conquest and control with power." The US and China are the latter. The UK's power has slipped, but it's still in this category with extraterritorial colonies. A specific emperor is structurally optional.
But the Chinese Empire has already fallen and changed radically, U.S.S.R. is not the same thing as the Russian Empire, even though they shared most of the same territory.
The point was that every empire falls sooner or later and that it happened to China as well.
