United States seems unfair since it only includes "America" in it's official name. I think Saint Kitts and Nevis should also be included too, because it's named for Saint Christopher.
Yeah, I debated whether to include the US. America alone is a pretty common term, and the demonym is "American", so I decided to include it. I do see the argument though that the most common name doesn't include the word America... As for Saint Kitts and Nevis, St. Christopher wasn't European AFAIK?