The rise and fall of great powers and their imperial domains has been a central fact of history for centuries. It’s been a sensible, repeatedly validated framework for thinking about the fate of the planet. So it’s hardly surprising, when faced with a country once regularly labeled the “sole superpower,” “the last superpower,” or even the global “hyperpower” and now, curiously, called nothing whatsoever, that the “decline” question should come up. Is the U.S. or isn’t it? Might it or might it not now be on the downhill side of imperial greatness?