The role of Protestant evangelicalism and fundamentalism in shaping US politics and culture is very important and often overlooked.
See my opus Dances with Devils for a look at some of the apocalyptic roots of this:
http://www.publiceye.org/Apocalyptic/Dances_with_Devils_TOC.htm
The best easy-to-read book is Martin, William. (1996). With God on Our Side: The Rise of the Religious Right in America. New York: Broadway Books.
-Chip Berlet