That's interesting. So U.S.-East seems the best option for supporting both the U.S. And most of Europe. Although if you're slightly less concerned about the U.S. Then the EU seems a reasonable conpromise.
One thing I doubt is the uniform ping times within countries. For example, do we really think ping times are uniform across the breadth of Russia?
0-300 is a pretty wide category, though; 300ms is not a great response time. Better would be to target 100ms. A logarithmic scale would probably have served better in the color-coded maps.
If you have a global market, and only want to operate in one region (a practical necessity for many people, given the technical challenges of doing otherwise), then US East is almost always the best option.
One thing I doubt is the uniform ping times within countries. For example, do we really think ping times are uniform across the breadth of Russia?