Thank you for working on this comparison. Historical comparisons are very tricky. In broad context they can be apparent but that is about as far as it goes. There are useful comparisons with the late, western Roman empire to improve understanding of the American empire’s collapse.
The most interesting comparison, I think, are the things that are different. The failure of the Roman Republic is very close to the American Experiment that had a loose republic structure. The traditional Roman aristocracy is very similar to actions of the US Senate that was designed for a landed gentry. Neither proved to be representative in the original Athenian form.
The Roman Emperor tracks very well with the American imperial presidency. Incompetency increased over time with a few capable people individually selected as successors. But the Roman legions and, specifically, the Praetorian Guard was the control for incompetent emperors. As things declined the less capable emperors with little real power were prone to ‘accidents’. We have no tendency to that yet.
Unlike the Western Roman Empire, American racism has prevented true diversity in the national leadership. The Western Roman Empire was disrupted by a variety of border peoples who were being recruited and integrated into the Roman Legions. These border peoples actually preserved the empire by moving it north. While the Eastern Empire finally fell and was replaced in 1453 by the Turks the Western Empire in form survived until the 20th century. This was the Holy Roman Empire centered in what is now Germany and Austria.
I’m willing to say that America will not have that type of survival. Racism and genocide doomed America from the start. That is the difference of a 300 year history and a thousand year Roman or three thousand year history as the Chinese have.