When the industrial age ended, some places took it better than others. Some stripped down major cities and built societies based on trade routes. Some claimed rich farmland and garrisoned it. However, some regions were just out of reach of the more powerful nations. There are cities in America that only exist due to transit for trains, automobiles and airplanes. Once these highly industrialized means of transport dissipated, way of life in the sparser regions of the map was changed drastically. Towns full of closely-knit families were cut off from the rest of the world, and these rural communities ultimately had to adapt. Because the land could not readily provide them what they needed, nor were they connected to any trade routes, the people here eventually phased out of a material life, and many outright gave up a stationary one.
The center of the continent is too cold, or arid, or both to yield vast populations and more complex societies. Those that survived were people who could handle whittling life down to the bare essentials--food, shelter, and clothing. (And very basic clothing that could cover one in the cold) These conditions resulted in a hardier people, who had to be able fight nature on its own terms. Caste systems were largely unimportant, because there was very little wealth one could acquire. There are no noble families here.
The leadership of the tribe usually depends on if it's in a period of war or spirituality. Elders usually interpret and guide the faith of the tribe, and most political decisions are made with the sanction of these elders. However, a lot of the meat and potatoes of decision making will go to a chief. He will coordinate raids on villages, wars with rival clans, and where to head when greener pastures await. In theory, the chief will be the son of a previous chief, however since the entire adult male population usually makes up the army, and there is no class system, leadership is contested fairly often. Grooming one to be head of the tribe is not significantly different from the way others are brought up. All tribe members usually fight the same way, nor is there there an administration one needs to be educated to run. Thus, an ambitious warrior can stage a coup, or an incompetent chief can be overthrown, with little to no difference in how things were run before.
However, some chiefs quite like the idea of having their lines head the tribe for generations to come, and aspire to have dynasties like those in the west. Their sons will be educated in history, sciences, and more sophisticated means of warfare. This has certainly helped tribal leaders become more central authority figures, but elders bemoan the corruption of civilization is slowly eating away at their way of life. The Canadian Kingdom, Greater Texas and Iowa Territory are made up of lands that are slowly evolving from Tribalism to Feudalism, in large part because of tutored scions wishing to emulate the monarchs. Much like the Gauls, Vikings and Mongols before them, eventually the old ways give way to the new.