Just in time for the new season of House of Cards, the Southern American accent comes back to the forefront of our minds via Kevin Spacey's performance. There are definitely debatable decisions on his and the production team's part to reflect Frank's upbringing from Gaffney, South Carolina but I think there are some key articulation choices that satisfactorily create the Southerner persona. If you are interested in the exact details, Vox does a good overview here.
Now there are multiple Southern American English accents depending on the specific region of the south, just like there are many dialects in the city of New York. There are some basic characteristics that are shared but to learn the specifics of a certain region, you do need to do more research into the cultural influences and their impact on that region's articulatory preferences.
For example, Louisiana is strongly influenced by a mixture of 18th century French, Spanish, Native American, Asian and African cultures. Before 1803, the region had been both a French colony and for a brief period, a Spanish one. Furthermore, West Africans were brought as slaves which eventually introduced the Creole influence. As a result, the French/Creole influence distinguishes the Louisiana accent.
The following infographic delves into specific sounds, phrases and grammatical differences that separate the Southern American accent from the typical North American accent.
If you have any comments/questions, let me know at firstname.lastname@example.org
BandanaMan814. (2013, Jan 04). How to Speak with a Southern Accent[Video File]. Retrieved from https://www.youtube.com/watch?v=jXhQhd_vq5U&t=4s
CZVids. (2012, Dec 31). Southern Accent [Video file]. Retrieved from https://www.youtube.com/watch?v=XPfOL4wUuMU
M.,R. [Rob M]. (2012 Nov 3). A Quick Lesson on Southern Linguistics [Video file]. Retrieved from https://www.youtube.com/watch?v=mNqY6ftqGq0