Both Protestants and Catholics have had a profound influence on American culture, unlike countries that are heavily skewed towards a particular type of Christianity like Italy (Catholic), Greece (Orthodox), Finland (Protestant). One of the main reasons people settled the U.S. in the first place was to establish religious freedom, as England had a state religion (Church of England) that discriminated against anyone -- Catholic or Protestant -- who wasn't a member of the "official" church.
As Catholicism has more members than any other organized religion in America, I would say recent American culture has been heavily influenced by Catholicism, but since Catholics do not have an outright majority, there is also other religious denominations who are having an major impact on American culture -- particularly in bible belt where Protestants dominate, and in Utah where Mormons dominate.
But the idea that "tradition" of America is solidly WASP and that Catholics are a tiny fringe minority in the U.S. is simply a fairy tale. It was true in 1776, but it hasn't been the case for over 100 years.
“But the idea that “tradition” of America is solidly WASP and that Catholics are a tiny fringe minority in the U.S. is simply a fairy tale. It was true in 1776, but it hasn’t been the case for over 100 years.”
I never claimed that.