Please give examples of satellite technology during Antiquity ... Will accept oracle's, magical devices we can no longer make sense of, and supernatural mental powers...
Regardless, Athens and Sparta were similar cultures, ethnographically. A better analogy would be Brittish Empire vs. American Colonies... Reconquista resulting in Ferdinand and Isabella overthrowing the Iberian Islamic Caliphate, or Andalus.
Due to virtual geological isolation, the likely downfall for the US oligarchy would be a sharp and violent civil war. They could afford to lose a variety of foreign adventures, in our highly technological world, without actually falling.