What separates Catholicism from Protestant and Orthodox beliefs?

The lack of a definitive teaching authority in the fundie church makes many individual fundies think that they have a direct line to God, notwithstanding all of Christian Tradition and the history of biblical exegesis (a "Bible, Holy Spirit and me" mentality). Such people are generally under-educated theologically, unteachable, lack humility, and have no business making presumed "infallible" statements about the nature of Christianity.