[MysticCat]

Assuming that by "to church" you mean to a worship service....

I would only wear letters to church in the form of a recognition pin on a coat lapel. I also would readily wear a red-black-gold tie.

Even when I dress down a little for church (polo shirt and chinos), I probably would not wear a shirt with any kind of organization logo on it.

Non-worship events at church would be a whole different matter. I have worn letters to quite a few church meetings/functions.