Anti-catholicism was a huge problem in the United States. Ever wonder why the Catholics created a whole parochial school system? One of the driving forces behind compulsary education laws was that the public schools would indoctrinate the Catholicism out of the kids, and turn them into good American Protestants, loyal to the President and not the Pope.
Anti-catholic bigotry was very real, and it's only been a generation since the dramatic shift in Evangelical attitudes towards Catholicism started.
For more information about this, read Mark Noll's Is the Reformation Over?. It's an examination of the interactions between the Evangelical community and the Catholic Church by one of the best evangelical academics out there.
He's a Catholic Apologist who almost finished building a raft to cross the Tiber.