The Peloponnesian war was arguably much more impactful than the Persian wars. It did affect the relations of production, almost 2 thirds of Athenian citizens died, and wages for craftsmen went from 7 liters of grain equivalent wich is sort of average for a pre industrial society to 15, Wich is insanely high. This kept slavery, and the associated superstructure economically viable. So no Peloponnesian war probably means Greece transitions away from a slave society into some form of tenancy much earlier. As well as greater efforts for Greek colonisation of Ukraine and the Mediterranean.

What impact does this have in the world? Probably not much. They would break away eventually and a new war between them may have the same demographic effect.

On the other hand a Feudal society may be more amenable to Persian rule, and may cause alexander to not exist. Making the empire last longer.

On the gripping hand, even if there is no alexander the empire is not going to last much longer either. There was an agrarian crisis shortly after Alexander's conquest, that would have happened anyway. so it's likely that would cause it's fall in this alt history, so at best they get 20 years more. And there would still be an Hellenistic world in the eastern Mediterranean afterwards.