I'm not that surprised by the results, especially given that it was about more religions than just one's own. Given the relatively low proportion of Atheism/Agnosticism in America it is largely confined to an educated minority. These people are far more likely to be exposed to other cultures and the concomitant religions. This in turn leads to a greater awareness thereof and thus the higher scores. Nor am I surprised by the high score of Jews as they are also exposed daily to a largely Christianised culture.