I'm not sure that you will receive a lot of support for the concept of a "cooler country" than the United States and personally I think a World Showcase that is absent the United States would be sadly and bizarrely incomplete. In the Epcot Model, it is my understanding that the United States is "hosting" the other nations, hence it's place in the middle, and so its removal would also complicate that model.
That having been said, there is space available elsewhere in the WS where new countries could be added, and I would love to see a few new ones join. My preferences would be Brazil, to represent South America, India, as the world's second most populous nation, and possibly someplace like Russia or Greece because they are really cool and have wonderful cultures.