If this were a different kind of forum the answer would be "Blue states lol."
If you really want to know about rationality, strictly speaking, though, I'd think of examples of irrational economic choices, and see how common they are, location by location. Look where people play the lottery the most; also look where non-professionals day trade. If you had a lot of time and great statistical tools, you might be able to calculate where hyperbolic discounting or loss-aversion is the highest.
On an easier (but less accurate) level, look at home foreclosure rates -- this is evidence of when people across the economic spectrum bet wrong on something important to their own lives. Betting right is almost the definition of rationality, isn't it?
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.