As well as Spain after Felipe II, US is a big empire beginning his decadence. The worst problem is not economic; the US citizens are falling into ignorance, and that's really bad because their own governments are promoting that. A lot of treads here are showing that to all of us: the US citizens believe that they are really good guys trying to save the world, killing only bad terrorists and narcos, helping poor countries to develop and grow, spreading democracy, and killing millions of humans, but in a better way than the other empires.
If you are a US citizen and you want to get good information about what’s really happening in the world, you will never find in all your masses broadcasting media nothing about the real intentions and actions of US, just propaganda to convince you that “there is nothing better than US”.
You are doomed: despite of the US decadence, you will be still a big country, but you are not a big nation anymore.