It was never ever specifically stated that Splash Mountain took place in Georgia. Even if it did, it wouldn’t matter much as the land wasn’t tied together by state geography, but instead it was tied together by visual aesthetic and time period (orange rocks, woodlands, 1800s America, American folklore, etc).
TBA could have been made with respect to these principles, but they actively went in the opposite direction. Green rocks instead of orange and brown. Jazz music instead of folk/bluegrass. 20th century technology such as a 1920s automobile. If there was any rule to follow, it would be that the Frontierland attractions are set in a time period that predates the invention of the modern car.