The U.S.A. is its own greatest nemesis.
By some estimates, the equivalent of the defence budget is flowing into the illicit-drugs black market. By some estimates, as much as one fifth of the population is addicted to opiates. Liberty is being legislated out of existence in the name of national security; innovation is being undermined by setting trade tariffs; robust action on climate issues is being undermined by outright stupidity; concerted action on a whole spectrum of issues (gun control, national health insurance, LGBT issues, abortion, teaching mythology as science in the schools, etc. etc.) has been mired in polarized acrimony for decades; cumulative foreign policy blunders since Reagan (dithering on the Palestinian issue, f(o)unding of the Mujahadin in Afghanistan who later mutated into the Taliban, the subsequent invasion Iraq and Afghanistan, toppling Col. Gaddafi with no plan for securing his successor, etc. etc.), have destabilised the entire Middle East and North Africa, and enraged half the world's Muslims against Western values .... America faces so many major problems, and with no political will to reach consensus solutions, I fear for America's long-term survival. At some point, even America's oldest and closest allies will jump ship. The U.S.A. will no doubt stagger on for another 50 or 100 years, consuming itself from the inside, while the Chinese quietly slip into the world leadership role without any fanfare.