When I look at Christianity I see the teachings of awakening at the heart of it. God is the absolute, unmanifest, whatever you want to call it. The rebellion of Lucifer and Adam and Eve's consumption of the fruit of the knowledge of good and evil (good and evil = dualism) is the birth of the dualistic mind (ego). The struggle for salvation is the struggle for awakening. Jesus is simply an awakened teacher; Jesus' teachings are very similar to those of other awakened teachers', though obviously communicated using the vocabulary and belief systems of the time.

The question of how the religion as we know it today came about is one for the scholars (obviously Christian mythology was heavily influenced by already existing myths), but Christianity has a clear nondualistic thread running through it. Obviously the Bible has heavy dualistic elements due to being influenced so heavily by Western philosophy, but I don't have to try hard to see the clear teachings of awakening at the heart of it all.

If you're interested, I hear there are lots of nondualistic commentaries on Christianity out there. Adyashanti's Resurrecting Jesus is one (though I haven't read it), Father Richard Rohr has some good talks on YouTube, etc.