The state serves to clearly define our collective goals and enact a set of rules that will foster progress towards these goals.
A state can allow societies to work together for the common interest of those in the state. As noted by R.J. Rummel, a state should not be confused with the political power, or government, of the state as those political systems can change over time. Many scholars and philosophers have discussed the connection between state and society. But it is namely the common goals of a society that makes the “state” its ideal expression. Aristotle believed that the state, city-state, could meet the needs and goals of a society’s culture, economy, politics, and religion. Society shapes one's beliefs and therefore one's goals. Societal groups within a state can work together to allocate public resources, protect the rights of citizens of the state, and allow people to organize for social transformation.
The state is not an expression of society, it is a crude parasite on societies’ backs. Society can be understood as the sum of all of our voluntary interactions with each other. We form societies naturally by interacting and connecting as individuals. The state grows off the back of these interactions and tries to impose limits on them. This isn’t an “ideal expression” of society, but a gross attempt to control society and the individuals within it.