I don't have the numbers on hand, but I recently read that a remarkable number of US Evangelicals regard each member of the Trinity as an autonomous entity. This might invite you to scoff at sola scriptura, but I can't imagine the numbers being better for other denominations.

It's a strange thought: how many, maybe most devotees are actually heretics, especially when you consider more remote cultures. I've been looking for fiction that explores this idea. I think Black Robe touches upon it, but I haven't seen it in two decades and could be misremembering.