There is no doubt that the U.S. is a major power and will remain one in the foreseeable future but other societies are forging ahead and restricting the relative power and therefore leadership of America.
Dr. Ferguson's theme isn't new. Root causes of the rise and fall of western civilizations were earlier explored by UCLA Professor Jared Diamond in his books Guns, Germs, and Steel, and Collapse in far more convincing fashion.
Among foreign policy mandarins here and abroad, it's become axiomatic that America must radically downsize its global ambitions to avoid hubris and to match our straitened economic circumstances. Hillary Clinton is having none of it.