No one but the most ignorant would have called a generic white person a WASP. It refers, as you said, to a minority of white persons in the U.S. It would, I believe, exclude people of German and Scandinavian descent, who make up a pretty good numerical and historical portion of the northern states.

The fact that many people did use the term WASP incorrectly shows how ignorant and insensitive they were, and it was probably some of the same ones trying to prove how sensitive they were on these issues.

mg