Hate to say it, but I'm not sure this type of visualization is ideal for this data. Given that the actual clustering is meaningless, I would think a simple histogram would expose the relationship between the different cities better.
My mind could be changed if this exposed a hierarchy, for example if the US was a single bubble which could be clicked-into. Or if there was a meaning behind the clustering, like if geographic proximity determined how close the bubbles were.
My mind could be changed if this exposed a hierarchy, for example if the US was a single bubble which could be clicked-into. Or if there was a meaning behind the clustering, like if geographic proximity determined how close the bubbles were.