Answer:
American Atheists, eh? Well, being one I would have to say they are Atheists who are more involved in promoting science, reason, and rational thought over religion. In other countries such as Sweden or the UK. You would not have to do this because most of the people in said countries already know how important science is. Giving them a higher percentage of non-religious people. Like the Reason Rally that recently took place in DC. That couldn't have been imagined in somewhere like the UK because they don't need a rally for reason. America is somewhere around 85% Christian, and 15% Non-religious. It is said that there are more non-religious because there are those who don't want to tell their families because they are afraid of what they might think of them. On the other-hand, Sweden is 85% non-religious and the UK 48% non-religious. And such rallies are unnecessary. All in all, american atheists are atheists who live in America and are subject to religious dogma more often than that of other countries.