In the northern states you'll often find furnaces, at least in older homes. In the southern states, it's pretty much all electric heating if it's recent (< 30 year old) construction.
We did have a neighbor who contracted with a propane company to fill a residential tank, which was used for heat and cooking. But that wasn't common in the neighborhood.
In Tallahassee, the places I rented didn't have gas, only electricity. Eg, pulling up rental housing in Tallahassee, https://www.rentrange.com/tallahassee-fl/o-3316-calumet-nice... says it has "Electric heating". Searching for Atlanta, I found http://www.cbs46.com/story/21444870/atlanta-fallen-tree-leav... which says "'Fallen tree leaves Atlanta residents without lights and heat' ... "My house used electric heat so it's cold".
Rather than be anecdotal about it, I found "Space Heating in U.S. Homes, by Climate Region, 2009" from http://www.eia.gov/consumption/residential/data/2009/#sh . Of the 19.1 million homes in the "Hot-Humid climate region", 12.4M use electricity, 4.6M use natural gas, 1.4M have no heat, 0.5M use propane, and the others (fuel oil, wood, etc.) are too small to be meaningfully reported.
There is an apparent conflict between your observations and this survey (and with my own observations from living in Florida).
GA has 1.7M homes heated with gas, and 1.7M heated with electricity, out of 3.5M. That has the highest percent of homes heated by gas.
In FL, and in line with my observations, has only 0.4M heated with gas, and a whopping 5.7M out of 7M heated with electricity. That's the lowest percentage, which is reasonable for a place with little need for winter heating.
Overall in the South, some 13.3M homes are heated with gas, 24.2M with electricity, 0.6M with fuel oil, 1.9M with propane, 0.8M with wood, 0.2M with kerosene, and 1.0M have no heat.
> Everywhere but Northeast, fewer homes choose natural gas as heating fuel
> EIA data show that homes built since 1970 use electricity and natural gas as their main heating fuel in roughly equal proportions.
> The South is the only Census region where electricity is the main space heating fuel in the majority of homes.
The survey data is at http://www.eia.gov/consumption/residential/data/2009/ .