In a POD after the 3rd Punic War but before the ascension of Julius Caesar to Dictator for Life, get the Roman Republic to fragment into several pieces.
Even before Caesar you have quite a few strongmen there who were dictatorial a si9milar manner.
I mean between 146 BC and 48 BC you have Marius, Pompey and Sulla who were all considered a threat to the Republic one way or the other. Oddly enough all three of them seem to have tangled with Mithradates of Pontus...
the 70s, 80s and 90s BC all could be a good fracturing point.
In a POD after the 3rd Punic War but before the ascension of Julius Caesar to Dictator for Life, get the Roman Republic to fragment into several pieces.