In addition to whatever differences in rationality level there may be between places, there are also significant differences in how you tell a person in a given place is unusually rational. (This is an automatic consequence of beliefs being correlated with geography.)
For example, atheism seems to be a much better filter for rationality in the United States than in Europe (where it is not nearly as much of a "contrarian" position).
What are some good regional litmus tests?
To ask such questions, you must first define a scalar measure of "rationality" that can be compared between people. I don't find the choice of this measure at all obvious, or even that it can be meaningfully defined.
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.