Is the world created upon 'balance of power' fading? Did these political system cause its own demise through state bossiness and the control and imposed limitations on weaker states. Although we now have at least four states attempting to climb to the top of an unrealistic power heap, only one, after the USA, can be said to be a serious contender. Russia is not a world power it just thinks it is, and has a failing economy backed up by imperialism amongst vulnerable states, its expansion as much a business model as Victorian type competitive imperialism. India stands waiting like a vulture on the edges of the present catastrophic developments.
Nation states still hold centre stage, the one continuous development of balance of power, but holding on rather than existing confidently in a spiral that may be gathering momentum. Terrorist groups that exist outside of nation but which maybe funded by them or often are independent actors able to gather large combatants within political or religious motives.
The realist understanding of Chomsky and Mearsheimer is long out of date in a world of political/business systems and floating armies. Using it as a tool of understanding creates confusion only!