Cycles of history
In fact, I find illusory “cycles” far less rewarding than the notion of “attractor states” … or pitfalls that seem relentlessly to pull in cultures, because of repetitive traits in human nature.
Oligarchic feudalism is one such attractor. (Find the exceptions: agrarian societies that avoided this trap. I can name only eight.) Another attractor is fear-driven xenophobia. Machismo is one more. Put a dozen or so of these together and you start getting a really good picture of our tragic history. (And yes, because these themes keep recurring, matters can thus look a bit cyclical. But that’s like saying the fundamental reason that a car moves is because the wheels turn.)
But leadership also matters, e.g. Athenian democracy did not fail till Pericles died, and then just barely. And that is where miracles keep happening to America. here America finds NEW attractor states … bad presidents are followed by good ones, citizenship triumphs (barely) over anomie and cynicism, and seminal decisions transform the world.