The inventors of the robots would be the most powerful people - and the programming to preserve one world while destroying all the others would be the paramount risk. All the worlds would have to have scientists on the team which builds them and the smartest scientist(s) would have a chance to con the others. The others in turn would fear just that very thing and secret research would always be conducted so as to be able to counter the robots defenses or make a first strike on the robot police ships.

It's a great movie. One of my faves - but the movie fails the reality test due to these things.

I love it when the reporter fails to get the desired hysterical/prejudicial response from Klaatu as they observve the craft and quickly cuts him off and moves on to the next person - that in a nutshell is the media of planet earth.

Best wishes,

SDAI-Tech1