They would look at the vast regions of the world that are peaceful, and think we are foolish for being so trustful of our neighbours.
"Why is Washington not afraid of New York raising an army and marching on the capital?", they would say. Until the last couple centuries, that's something you'd have to be afraid of. Yet, that's something that people today would think is preposterous.
I'm an optimist. I happen to think this is a trend that will continue.