One of the most recent surveys about American attitudes toward atheists is one carried out by the University of Minnesota. Some results:
When asked to identify the group that "does not at all agree with my vision of American society":
Conservative Christians (13.5%)
Recent Immigrants (12.5%)
Responses to the statement "I would disapprove if my child wanted to marry a member of this group":
African Americans (27.2%)
Asian Americans (18.5%)
Conservative Christians (6.9%)
Whites at (2.3%)
Gallup polls also consistently indicate that about half of Americans would not vote for a qualified candidate for President if they knew he/she was an atheist.
Here are the percentages of people from the 1999 Gallup poll saying they would refuse to vote for "a generally well-qualified person for president" on the basis of some characteristic:
Would you be upset, angry, and/or worried if you lived in a country where nearly half the people said that a member of a group with your religious views didn't share their vision of the country, didn't want you to marry their children, and wouldn't vote for a member of your group for President?