Emerson was also non-Christian, but his praise of self-relance fused Enthusiasm and gnosticism into the "personal relationship with God" embraced by Evangelicals.I will not live out of me
I will not see with others' eyes
"We live amid hallucinations," Emerson wrote. And the hallucinatory nature of Evangelical Christianity supports this claim. The Enthusiasm of ecstacy, glossiolia, and communal trance is fundamentally anti-intellectual. But it reflects the Amercan worship of the individual.
I'm sure there are other reasons for the popularity of Evangelical Christianity in the U S. This may be one of them.