Humans have a proclivity for norm following that is grounded in the emotions rather than in reason, and consequently a tendency to invest mental models and the rules that flow from them with intrinsic worth. ~ Francis Fukuyama
Life in society proceeds in an orderly manner owing to norms. The most important mores are taboos, such as not killing or stealing. Sadly, people in one culture may not extend the courtesy of these norms to those in another culture.
The term social control refers to the shared understanding and rules that constrain public behaviors. The wide array of norms which permit a society to achieve relative peaceful social control is called its normative order. The punishments for violating norms are sanctions.
As social structures begat institutions that garnered leverage in societies, social stability became entangled with the vigor of governance. Throughout history, polity invariably both reflected and defined social values.
When institutions faltered societies suffered. The Roman Empire exemplified the decay of institutions which lead to the collapse of a civilization.
Often, societies invaded by outsiders softened themselves up through the internal corrosion of corruption. So went Rome before the Germanic tribes arrived en masse.
Societies have had various degrees of uniformity or diversity in their cultures. In relatively stable societies, there is a dominant culture from which is drawn the ruling elite, with token representation from the other major cultures within.
The United States today is an example of a mature, modern society that is a vast mixture of cultures, owing to its immigrant history. A militarized police state maintains order. The US is a superb example of conflictism in gut-wrenching action.
Though a society may be a geosocial umbrella for several cultures, those cultures share important values, or are otherwise riven in time from cultural conflict. The history of China is exemplary: of both cultural integration and sporadic disintegration. China also illustrates the territorial conquests that were common throughout human history in shaping societies, where cultural conflict was incidental in the impetus of upheaval, and quest for power by cliques the driver.