History teaches that nations outlive empires. Canada has survived the decline and fall of the French and British empires. What destroys empires is imperial overstretch, the unwillingness of rulers to understand the limitations of their sway. That is the likely fate of the American Empire in the 21st century.
It seems worth recalling what differentiates a hegemon from an empire.
Empires typically conquer neighboring countries or coerce them into political union; claim sovereignty over their acquisitions and rule them from the center; demand tribute or otherwise expropriate human and natural resources; and displace native elites with colonists loyal to their homeland and draw foreign elites to the core. In the past century America has invaded or had military operations in a number of countries in the past century (Japan, Germany, Philippines, Grenada, Panama, Haiti, Korea, Vietnam, Somalia, Kuwait, Afghanistan and Iraq). None of these countries can be said to be a part of the US polity or to pay tribute to the U.S. On the contrary, the U.S. has invested vast amounts of blood and treasure to preserve or enhance the freedoms and prosperity of its allies and (former) enemies alike.
To my mind, a more appropriate term to describe America's undoubted economic, military, diplomatic, cultural and technological preeminence is the term "hegemony" which my dictionary defines as "a preponderant influence or authority especially of one nation over others".