This map was in the September issue of Diabetes Care.
Diagnosed and Undiagnosed Diabetes Prevalence by County in the U.S., 1999–2012, Diabetes Care, September 2016

Age-standardized diabetes prevalence by county, 2012. A: Diagnosed diabetes prevalence. B: Undiagnosed diabetes prevalence. C: Total diabetes prevalence.

This was interesting:

However, our estimates of diagnosed diabetes, which are based on data directly observed at the county level, suggest that there is more variation in diabetes prevalence among counties than can be explained by socioeconomic and demographic differences alone. Further, the underlying factors driving differences between socioeconomic and demographic groups have not been entirely elucidated. Given the significant health and financial burden of high diabetes prevalence, this disparity demands further investigation into what underlying (and potentially modifiable) factors drive the exceedingly high diagnosed and total diabetes rates found in many communities.

As you can see, there is a whole lot of variation across the US. If what people eat affects their risk for diabetes, what do you think people are eating in the South, especially the Southeastern states, that are making them more prone?