It's on "This American Life", a syndicated radio show broadcast on public radio stations.
It has its own website, http://www.thislife.org, produced by WBEZ in Chicago. They sell the episodes to individual stations, so the show isn't broadcast in all markets, nor at the same time in the markets that carry the show.
In the black frame on the left of the screen, you'll see "Episodes/RealAudio, by year originally produced". Click on "05", and look for "Godless America" by scrolling down in the frame on the right.
Many of these shows are worth a listen. TAL is unique.