Great question, Heather. For some reason my mind always combines South and Central America; I don’t know why. 🙂
One of the reasons it’s grouped that way in the Visits to . . . series is because I thought we would need the better part of a year to learn the 50 United States. So it seemed to work out well to divide it the way it is. But now that you guys have pointed out that Central America is officially part of North America, I feel a bit sheepish. Sorry for the confusion.