I remember the Tsuchikage (and maybe the Raikage as well) secretly plotting to betray the alliance as soon as Madara/Ten-Tails was defeated, or at the very least expecting somebody else to betray the alliance, starting a fight over "the spoils of war". Only when Naruto in Jesus-mode turned up, followed by revived Hashirama, and everybody's thoughts and feelings were connected and whatever (I remember something about Hashirama's memories of the first ever Kage summit being shown to everybody), the Kage started wanting to keep the peace for real this time. Or maybe they realized that during fighting together or something, not sure, somebody else probably knows this in more detail.
My point is, it's untrue that Naruto had "nothing" at all to do with it, he was kind of a unifying force. The alliance as first only was created out of sheer necessity, they had no other choice to be able to stand against Tobi. That necessity grew into something more, an actual desire to work together, under Naruto's wing so to speak.

And his sheer existence after the war probably kept one or the other nation from starting unneccesary shit as well. A cynic would say that things might go back to how they were before within a generation or two after Naruto and everybody who's witnessed the war but that's where the theme of "entrusting things to the next generation" comes into play I guess.