That's actually not a bad idea but something like that would only work if every country in the world agreed to break up into city states. Something which is unlikely to happen. Any country that stays whole would hold power and control over the smaller independent states. There is a reason why every country tries to lay claim to as much land as they can. Not everyone wants equality. In such a scenario, independent states would likely have to unite into bigger entities to better counteract pressure from the countries left whole. And we're back to square one.