GregF, Sorry I failed to respond to your question. Perhaps this will help. Based on 1990 statistics and I checked with 2001 stats and its about 76.5% now; but I cannot find a link to use and i'm in a hurry to go out.....
Christianity 151,225,000 86.2%
Nonreligious 13,116,000 7.5%
Judaism 3,137,000 1.8%
Agnostic 1,186,000 0.7%
Islam 527,000 * 0.5%
Unitarian Universalist 502,000 0.3%
Buddhism 401,000 * 0.4%
Hinduism 227,000 * 0.2%
Native American Religion 47,000 --
Scientologist 45,000