Here are 3 ideas I came up with:
I was trying to visualize the problems, which brough down Roman and British empire, into a monster going for the USA.
A jenga metaphor of the danger of expansion. The idea that we have decided on.
The evolution of empires.
Chris and I were both fond of this idea but there are too much details for the op-ed spot. I am thinking of making it into a poster. Chris suggested I can leave the last step of the USA evolution blank, I think that's really smart. "Say more with less" and " don't underestimate the readers"were the lesson learnt.