The process of categorization must balance the objective of accuracy with the objectives of usefulness and ease of use. Religion is one of the ways we can categorize people, and is especially useful when we can categorize a person by the specific faith community they participated in while living.
My own denomination, United Methodist, is organized by districts, annual conferences and jurisdictions, which somewhat resemble -- but often overlap, counties, states and countries. Accuracy would say that local churches would be categorized by the church structure. But the normal genealogist categorizing a great-grandfather is very unlikely to know the church structure, the effort to categorize would be abandoned, and errors would be magnified. I propose, therefore, that at least for United Methodists, we group congregations by the civil structure: Category: United Methodist Churches, Maryland; Category: United Methodist Churches, New Mexico.
What are the pros and cons of doing this?