And you'd be wrong. At the time in question, the only Christians WERE Catholics. You Protestants came MUCH later.
So called Protestants came along because the Catholics got so far away from the original Word.
For others reading this, study and learn that the world was never divided into only two, namely, Catholic and Protestant. The very idea that nothing but “Catholic” existed between 29 AD and 400 AD is a big perversion and re-writing of history.
There are millions and millions of Bible-believing Christians who have never been “Protestant” (at least not in the Geneva sense of the word), and the same number who have a history (or better, heritage) never connected with Catholicism (by the Vatican definition, especially).