The distinction between Protestantism and Catholicism is enormous; go and read about the five solae.
That is your personal opinion, someone else might not think these differences are enormous and like I said, both groups share mythology and tradition.
To consider the various branches of Christianity to be at all similar, even if historically accurate, is theosophical nonsense.
Never said they are similar, I said they are all clearly the same religion, a hindhu that is a cannibal and woreships kali by killing people, is still operating within the same mythology and tradition as a buddhist who is a vegetarian and holds all Gods to be imperfect.