Well, there are people who are dead serious about their religion in the USA, such as my friend Mark Stansbery who goes to church every sunday and has been part of not only the religious left but also the Left in general. He's been politically active on most important issues and stands _to the left_ of many (most?) men on lbo-talk on questions of abortion, rights of queer people, anti-racism, anti-imperialism, and so on. He's a union man, too, and he's been involved in many kinds of labor solidarity activities. I have deep respect for what he does daily, which maintains a diverse network of organizers and activists, secular or religious, in Columbus, OH. And Stansbery says that his politics--especially with regard to class + economic justice but also about gender, race, etc.--is deeply rooted in his understanding of God and reading of the Bible. (He's read Marx, Lenin, etc., too.)
However, people like Stansbery is very very rare.
Most Americans' relationship to their religions, churches, etc. is pretty _consumeristic_. And those who are actually involved in religions _know_ this; the opportunistic among them turn their places of worship into entertainment centers, while the more socially conscious ones struggle to retain meanings + keep their congregations together, in the age of Christian rock, 'religious' bumper stickers, megasuburban churces, and so on.
Religion in America can be as alienated, consumeristic, and lonely as other mass cultural products. Just think of those who watch TV evangelists and give them their hard-earned dollars.
Yoshie