Let us take Rome as an example. That empire was cleft in two before the "fall" of the Western empire, the Eastern lasting another thousand years. But within the West the model reduced itself from an immense system dependent on external sources for both wealth and food, to a more fractional model built on manors and city-states, each more or less self-sustaining. Even within the city of Rome the Goths maintained much of the civil infrastructure until the Greeks threw them out in the 6th century. Throughout it all the Church endured. None of these component elements was the old empire but despite that incredible 90-day period during the Gothic Wars when Rome was nominally "empty," Rome endured as well.
Let us consider, as the author did, the Soviet Union. There too centralization failed, spinning off a cloud of ex-clients. There too the ability to project some sort of imperial force was lost. There too the component parts coalesced around something that is proving quite formidable. It didn't "fall" any further that Rome did, albeit much more rapidly.
What does this imply with respect to an American "empire" that isn't really an empire at all? That turns out to be a bit more difficult to model, because ceteris paribus is too much of a stretch. But if what we have to look forward to is, broadly speaking, a decrease in centralization, an increase in regional focus, a diminishing of the ability to project power, and an increased necessity for self-sustainment, then we discover that much of this is already incorporated into the country's history. We've been there before, in short.
Just the other day I was telling Mrs. Redangus that I thought we were seeing the end of the concept of centralization. I felt the days of to big to fail were rapidly becoming to big to sustain. I believe we will be seeing more of a move towards decentralization in the future.
But consider how fast the British Empire went from #1 to third rate power.