I doubt there's any kind of real answer to this question. On a side note since others have mentioned places outside of Alabama where they have encountered Bama fans.....I was stationed in Germany from 1990-1993 and met many Germans who vacationed in Alabama and were Alabama fans. During the 60s & 70s many Germans were familiar with and had access to AFN which typically aired one game per week. Often, that game was an Alabama game. I went to a bar called the "Alabama", bought a lot of gear in local shops, and met many Germans once I returned home because I could pick out their accent when I heard it and I would ask where they were from.
I don't know about nationally.....But I'd say we're definitely top #3 on a global list of favorite college teams.