Comment by urbsgpw

Probably requires incredible amounts of energy to maintain an equilibrium like that over any prolonged periods of time. Maybe a feature of human societies that makes it improbable for any one society/state to dominate over longer stretches of time. Or it could be I just have the US, the UK and the roman empire in mind because I'd need more attention and I'm hallucinating the most probable answer based on my training data and your prompt. Very Cartesian, I know.