The South, in particular, has a deep tradition of singing that goes back generations and impacts our love of music and singing in the South today. Traveling singing schools were part of the Southern social fabric and their influence lasts to this day. Resembling old tent revivals, the singing schools taught skills such as singing as well as music theory, and they also served as community social events. The schools would last a few weeks then go to the next town or city. I imagine that once on their own, people would use their newly honed skills to write and perform songs about what they knew best. Among those topics would be home, the state where they lived. That's where the size of the state is important. Georgia is a pretty populous state, and when you have a lot of people from a place there will probably be more songs about it.
Look at population -- and specifically the population for the 10 most populous states (current figures): Texas, Florida, Georgia, North Carolina, Virginia, Tennessee, South Carolina, Alabama, Louisiana, and Kentucky. There are lots of songs about all of these states except Florida and Virginia.
Tradition and population. That's my best guess. As beautiful as they are, you sure don't find anyone singing about Vermont, Maine, the Dakotas, or Delaware, do you? Alternative ideas are always welcome.