When I think of Yankee, I think largely of New England snobs. The folks from the Southern region of our country often blur the Yankee label by indicating anyone born above their respective northern state boundry (or the Yellow river if your in Texas).
In summary, I think Rockwell is nailing the Yankee mindset and its cultural influence on these great States. Yet, arrogance and greater-than-thou-ism is a human trait that can be easily acquired by any culture.
Kennedy was not a Yankee nor are the bulk of the New England snobs
A true Yankee is a descendent of the original New England settlers (I.E. the pilgrims)
The thing is the bulk of them did not end up rich snobs
The average Yankee is/was a taciturn working man/farmer
My dad was a classic Yankee an grew up as a poor farm kid
In my part of the South- panhandle Florida, those who hale from the southern parts of the state are generally recognized as yankees. Actually they are mostly from New York.
If you read the article, you will find that Wilson goes out of his way to point out that his use of the term "yankee" specifically applies to a certain type of new englander and new englander outgrowth, and not all northerners in general.