Every state was rife with division. As long as humans were individuals, they always found ways to disagree with each other.
A dispute could revolve around something as trivial as the color of a uniform to something much more influential such as the prohibition against arming warships!
No single human completely agreed with the stances of another human. It was impossible.
Billions and trillions of humans existed in a typical state. How could all of their relationships possibly remain stable with each other when every single one of them represented a source of instability?
The reason why many societies hadn't fallen apart was because a lot of rulers and governments had become quite good at manipulating their own people.
Nationalism, education and scapegoating were only a handful of the tools that officials used to unite different people and prevent them from clashing against each other.