If it’s as inaccurate for the rest of the country as it is for Iowa, it’s just made-up.
Far more Cardinals (and Royals) fans in Iowa than indicated here.
But, if accurate, it proves MLB idiocy as the Twins, Brewers, Cubs, White Sox, Cardinals and Cubs all claim Iowa as home territory, most with no fan base of support.
It’s based on Facebook team followers and zip code.