The fall of Rome was slow, devastating and changed the course of history. With all luck the decline of the American hegemony will be a far smoother transition. I may even grow to miss the American overlords, the the world with China at the helm will be a far less welcoming place. even though the Americans were not the most principled or even effective police of the world, the rule was never Imperial in nature and at the heart of its policy was a genuine concern. This will not be the case in the next two decades when China comes to power and will be tempted to use its influence in shocking ways.
Today American politics is a mess to look at, special interests have embedded themselves within the government and the philosophies of the major players is as skewed worldview as anything that would be said by a feudal baron. The government is corporatism, anti-civil rights, and the worst kind of religious. Although the problems of stupid governance are worse in the Republican Party they are by no means limited to it. In order for it to maintain its standing it will no longer be able to rely on military might and will have to rely on it’s voice. Hopefully this realization will be sobering and snap Americans and their idea of American exceptionalism back into reality.
Maybe America will fall like Rome, or maybe it will fade gently into the background.