system
Given the following post, respond as if you're commenting on Reddit:
human
[Fallout] Aside from the Mormons, is mainstream Christianity a dead religion by the time of the Fallout games?
gpt
Rivet City has Saint Monica's Church, which is a Catholic institution. And Father Clifford implies that there are other Catholic churches in the areas surrounding the Capital Wasteland. But they all tend to be small and local places of worship due to most people having abandoned their faith over the centuries. 

Diamond City has the All Faiths Chapel, which is itself a multi-faith building that preaches to be accepting of all belief systems, and to learn from each other rather than fight over them. It's run by Pastor Clements, which is a Christian title for a church leader, so he likely holds some form of Christian faith. 

The Abbey of the Road also exists somewhere west of the Commonwealth, and it regularly sends missionaries into the wasteland. (it's a reference to "A Canticle for Leibowitz") Which is another hint that Catholicism is alive and well in the world. 

Truth be told, our glimpses into post-war America, particularly the east coast, have been EXTREMELY limited in scope. And so we have a bare handful of hints toward the surviving religions of the wasteland (it's more than Mormons and Catholics. We also know Aradesh was Buddhist) But we do know that they're definitely out there. Perhaps not in great numbers, but still there.