Let me suggest you first start with the definition of Catholic as used in the Apostles Creed and then work it out for yourself. I stated a fact, I am not going to hold school on theology or Roman Catholicism. But, I stand by the statement: "Catholics are Protestants, but Protestants are not Roman Catholics."
If you can show me, via Scripture and the non Roman Catholic Creeds where I am incorrect, go for it.