Think a new "dark age" ...

... is just around the corner? Well, maybe you should bone up on your history: Decline and fall of the Roman myth.
"Caparisons are odorous," as Dogberry opined, and historical parallels tend to be superficial. The "American Empire," such as it is, has more in common with Athens's than Rome's, actually. Like Athens's, it is fundamentally mercantile - after all, it isn't American armies that have invaded France: It's American movies and fast-food joints.