Christianity.

[Diana]

I think it's less that Ra "supports" Christianity and more that the vehicle (Carla) was already imbued with that religious framework, and thus they used Christian examples, talked about Christianity for that reason. If the channel was Muslim, it would be different methinks. Same for Cayce 

just one small slice of one perspective

I think what those of Ra supported above all things is free will. In that regard, they supported Carla's devotion to Christianity, especially in that while channeling, her strong belief system was beneficial to her tuning and ability to clearly channel.

The largest portion of the Earth's population is some form of Christian. Therefore, it makes sense that those of Ra would use examples that speak to the most general thinking of the time. And I agree that the channel is an influence in what comes through—even when it's done unconsciously—so Carla's beliefs would be relevant there as well.

Found this on Google:

Christians—2.2 billion followers (representing 31.5% of the world's population) Muslims—1.6 billion (23.2%) Non-religious people—1.1 billion (16.3%) Hindus—1 billion (15.0%)

 
Of course there is more such as Buddhism, Judaism, and indigenous spiritual beliefs.