So, if not one world, how do we keep from blowing ourselves up?

This really is a continuation of yesterday’s post and a new topic in one.  The comments to that post indicate a concensus that “one world government” is a Utopian pipe dream.  Some commenters even suggested that it was desirable to have many smaller countries.  Okay, but we do have the capacity to blow humanity off of the face of the earth.  The more nations we have, the more people who will have that capacity.  Assuming that we don’t want to blow humanity off of the facce of the earth (and, gee, I hope that’s a safe assumption) what do we do to prevent that from happening?

And, in that is really two questions.  What do we do in the short term?  And what do we do in the long term?  For the second question, what will the world look like in 100 years, or 250 years, or a thousand?  If Wells’ dream is false and we are not moving toward a united world, what are we moving toward?  As always, I’m eager to see your ideas.