"The south" is an entity that is more or less defined. "The North" is a number of seperate regions that all just happen to be NOT "The South"

"Old Cape Cod" - which applies to a spit of land that barely rises above sea level and is only 60 miles or so long can certainly be described as "regional" - but it's a pretty small "region".

Of course any Cape Codder will tell you that the Cape is the most important region in the US - ;)