Some weird things I've noticed while playing around with the map:
Just west of Dallas, there are two counties where the third favorite team is the Cubs.
The Cubs, in the 1980s, became a nationally-popular team due to their broadcasts on WGN (which most cable outlets at the time carried). The Rangers were a dumpster fire back then ... I bet this map circa 1980 would've showed the Astros owning Texas pretty handily.
I know at one time (mid-80s or so), the Cubs were #1 in New Orleans (N.O. had no minor-league team then). Then the Astros started broadcasting three/four games a week in New Orleans, and carved out a good sized niche in the Crescent City as well.
Check New Orleans for me, if you don't mind. I'm guessing bandwagoners have shot the Yankees & Red Sox pretty high locally, while the Astros & Cubs still have a presence. Though the AAA Zephyrs are a Marlins affiliate, they seem to have no following at all locally.