This is what I want to say about denominations:
The 23 Churches that are in communion of Rome, and which make up the Catholic Church have a membership of around 1.15 billion people.
To put things in perspective, lets just say the Catholic Church has an even 1 billion people as members. This means, if your Protestant denomination has 1 million people in it, this is .01% of the size of the Catholic Church. If it has 10 million, this is 1% the size of the Catholic Church. [The Southern Baptists have 16 million members, so 1.6% the size of the Catholic Church.]. 100 million would be 10%.
This is a factual list (though a bit dated) of all the world’s religious denominations (not just Christian) that have at least 1 million members:
adherents.com/adh_rb.html
So… the Catholic Church has 1000 million out of roughly 6000 million of the Earth’s population (1/6 of the world’s population). But, if you get down to a Church with 1 million members or less then that is 1 million out of 6000 million. Or 1/6000th of the world’s population.
It makes sense that such Protestant churches would teach that the Body of Christ is not limited to a single denomination, and can be spread across a wide array of ‘true believers’ even though they may differ considerably in terms of doctrine.
I just want to point out how fragmented and scattered the Protestant Churches are, and how unified the Catholic Church is. Make of it what you will.