My guess is that the correlation is with poverty rather than voting preferences.
As a former Mississippi resident (and one who did not have a passport until the age of 26) I can tell you I personally knew very few people who could afford to travel. The wages in the state may match the low cost of living, but a plane ticket is going to be the same leaving from Jackson Mississippi as it is LAX.
When this was posted on Reddit quite a few people used it as an opportunity to take jabs at how ignorant people in the south are because they did not "want" to see places outside our borders. It's quite difficult to do when a ticket to Europe would equal an entire months salary for many people.
