There is a reason that the world isn't run by a single person, why separate countries succeed, why most countries share authority with smaller sub-governments (state and local in the US. There's a reason why each species isn't a single superorganism, but individuals within species tend to cooperate.

"Life", evolution, or survival of the fittest -- clearly isn't a zero sum game. Over billions of years it's clear that it's positive sum. Blindingly obvious.

Adjacent governments too may well fit the bill. Too much competition can suck all the excess value out of the situation, but so can too little. The ideal form of government might be an angelic dictator, but you don't see the world full of them, do you? Healthy competition can find the optimum much better than singular good intentions. Partially because it allows experiment with real world results. With n=1 you can enact policy but you can only guess what effects it might have had because you have no control, no basis for comparison.

It's all about _healthy_ competition, and it's the basic idea that our republic was built on which can be seen everywhere in the constitution.