It could be a slow death, with something else landing the fatal blow.
Rome survived Nero by more than 300 years.
It's widely believed it was the dilution of their coinage that eventually brought Rome down.
The United States may still be the strongest nation militarily, our forces are not overwhelming and unlike the Romans, we have not been ruthless. At the turn of the 20th Century, we were far more severe against the Muslim rebels in the Philippines than we were a few years ago against Muslim rebels in Iraq and Afghanistan. No hand wringing or verbose justifications for waterboarding, the military just did it en masse, and much worse.
Over the last quarter century, there has been no great power with the ability to challenge the United States. The same could have been said about Spain at the apex of its power. Then the Spanish Armada was defeated. England and France arose as roughly equal powers to Spain with their own colonial networks and military interests.