There are many Religions spread out across Amestris, some with fewer difference then they would like to admit.
However, two stand above the others.
The Murusials, generally nicknamed Wallists. Believe that the great walls errected around Amestris was made by God, in order to protect us from the barbarians of the world. These gained in power greatly during the plague, due to saying that the plague was God punishing us for not valuing the freedom we had been given. Many believe that the God that Murusials refer to saved us from the plague. In some parts of the world, most specifically the West and North, the Wallists are generally wagabonds, and street urchin.
The Murusials have no quarrel with the magical theories, or Talents at all.
The Purists, believe in the ‘original’ God, displayed in the bibel. They believe that around 1500 to 1600 years ago Gods son, Jesus, walked the earth and took on our sins. They also gained power during the plague, for saying that the plague was a way to weed out those who was without faith. These highly oppose magic, and the theory that everyone possess magical properties.