David,
Martin Luther was a Catholic monk, John Calvin was raised Catholic,
Henry VIII was a Catholic King.
Protestantism came out of Catholicism, and to a greater or lesser extent
kept most of the doctrines, and the trappings and traditions of Catholicism.

For a thousand years, until the schism between east and west over the
papacy, there was ONE Christian Church.
It was another 500 years before the Protestant Reformation.

Our differences however, are non-negotiable, and the Catholic Church will
NEVER abandon its unGodly and unBiblical traditions and abuses which
caused the Protestant split in the first place.

That doesn't mean we can't witness to individual Catholics,
and let the Holy Spirit work on their hearts.

At any rate, most of the Protestant denominations in America are becoming
as apostate as the Church of Rome, and even worse; so we should
hold fast to the Bible, lest we be dragged down into apostacy too.