beef, Pennsylvania may be north of the Mason-Dixon line and was a major part of the original 13 (British) colonies but has its differences from those further north. If you read the post made by
Felix, he mentions the direct colonial reason for anti-Catholicism. However, not all constituents of the colonies were English and many of the Native Americans, due to previous contact with the French, did adhere to Catholicism. During the American Revolution, there was also a large increase of French (particularly, French Canadians; France allied with the colonies, I'm sure you know) whose religious claim was Catholic.
However, the more current excuses amongst those of the 'protestant' claimants relates to the counterclaims against what the Catholic authorities of the now distant past had charged as heresy. I've been associated with both camps; much of my original theological study was Catholic but I was eventually certified by a 'full gospel' organisation, many of whom are quite well anti-Catholic (whereby my tongue is very short now: bite, bite

).
