One part of mutually assured destruction was that nuking the shit out of one country would cause a global nuclear winter which would / could kill 90% of the population - even without retaliation. That's not as much an issue if there's a healthy self-sustaining colony on e.g. Mars. Nowadays what keeps the world reasonably stable is mutual trade dependency, up to a point anyway.

"All of which is happening in the Solar System..."

"All of which is happening in the Milky Way..."

"All of which is happening in the Observable Universe..."

It's probably a cycle that will occur as we make advances in communication technology.

And a long time before now:

"We want to get as fast as possible from one place to another; to get rid of space and to get rid of time. And the result of this is, of course, that—as we get rid of space and time, as we make all places almost immediately accessible by jet aircraft—all places become the same place. So naturally, the tourist who is beguiled into taking a holiday in Honolulu asks, "Is Honolulu still a ‘somewhere else?’ Is it still a land of girls in hula skirts, and naked breasts, and palm trees, and luaus, and so on?" Well, they’ll make it like it is, vaguely. But, of course, it isn’t. Honolulu is the same place as Coney Island, Atlantic City. Tokyo is just the same, it is simply an extension of Los Angeles; one of our suburbs. Because the faster you can get from place to place, the more you have conquered the limitations of time and space, the more everywhere is the same place. So the differences between different cultures, the differences between people, the things that we want to see when we go to foreign places are increasingly unavailable, except as something provided in a phony way for the entertainment of tourists to deceive them into the idea that they really did get somewhere else."

- Alan Watts, sometime before his death in 1973, in "A True Materialist Society" - https://www.organism.earth/library/document/131 , and other talks.