A very reliable differentiator as to whether an "American" is a Northerner or Southerner is the way they pronounce the word "greasy." If the "s" has a "z" sound, they're almost always a Southerner, and if the "s" is pronounced with an "s" sound they're almost always a Northerner.
Totally worthless, of course (unless the Civil War erupts again, I guess), but it's kinda fun, regardless.