To ask such questions, you must first define a scalar measure of "rationality" that can be compared between people.
Not necessarily; there just has to be an ordering. Clearly people's rationality can be compared, as extreme cases illustrate: Eliezer Yudkowsky is more rational than Kent Hovind, for example.
Sure, but very extreme examples aren't interesting. The real question is how many pairs of individuals (or groups) can be covered by that partial ordering. Not very many, I'd say, unless your definition introduces some criteria for which there is ultimately no rational justification, in any meaningful sense of that word.
Are certain areas of the world, specifically within the United States, more or less rational than others? If so, which ones and why? I am trying to determine what parts of the country would be ideal for me to live in the future and any help would be greatly appreciated.