Actually NASCAR is the largest spectator sport in the US, and most of the new super speedways are in places other than the south.
You sure? It certainly doesn't seem to be talked about by the general public as much as football, basketball or hell even boring ol' baseball. The news rarely reports on NASCAR stuffs. Their videogames games don't sell as well as the NFL and NBA stuffs. To me is seems like a backwater spectator sport that only poor people watch.
Some key facts: 1 in 3 U.S. adults, or 75 million people, and countless kids are NASCAR fans. Roughly 40% of fans are women. The sport has become the No. 1 spectator sport, and 17 of the top 20 most attended sporting events in the United States are NASCAR events. The sport is broadcast in 150 countries, and it is the second-most-watched sport on TV (after the NFL). NASCAR’s current eight-year TV deal began in 2007 and is worth $4.5 billion, or $560 million per year. The largest NASCAR tracks can accommodate upwards of 190,000 people in the stands and infield, far larger than any non-motorsport venue in North America. NFL stadiums, by contrast, hold on average 60-80,000 people.
http://www.forbes.com/sites/steveodland/2012/02/27/nascars-back/#57a99cf21c1dThe article is from 2012, but I believe the facts are still relevant.