Hard to say. As for Roman conflicts there's the conflicts with Carthage and Macedonia. And there's the Genkō War or Nobunaga's move to unify Japan if you go East. Central American conflicts ranging from conquistadors to the rise of communist regimes. Hell, the Cold War in general.

There are a lot of ways people ended up with similar worlds that are just a little off. It happens a lot here. Some even have the same people, but an alien or a machine or a disease twisted events into a different course for one. It stopped matching the other.

[This might take a while.]