California with “average†is surprising but note Nevada. For a state where Mormons dominate politics, that's pretty amazing.
CA surprises me a bit, but there are a lot of Hispanics in CA, and they are heavily Catholic and Evangelical.
As for NV, BD nailed it. Las Vegas and Reno have a strong religious minority, but they are a
minority. The segments of the hospitality and entertainment industries that are strongest in Las Vegas and Reno probably don't attract many church-goers, nor, likely, are many workers in those industry segments.
New England is lowest ... not much surprise in that. Much sadness, but not much surprise.