What might be the cause of the perceived difference between the atheists/nontheists in Europe and in the USA?

I have the general feeling that the average atheist in the USA, when asked about religion, will be very open about believing religion to be either evil or ridiculously stupid, and will make at least a few remarks about how idiot those lunatics must be who believe that there are invisible people living on the top of the clouds. On the other hand, in Europe you are more likely to hear that "well, I'm not very religious", but many would culturally still identify as a Christian, and will held marriages, child naming ceremonies, funerals etc. in a church, and might even rarely, but occasionally go to church on a bigger festival (like Christmas) because it looks or feels nice.

I wonder why. I know much more Europeans than Americans, so it might be that the louder voices are better heard from a group I have less contact with, or it might be that because in the USA the Christian fundamentalists are louder than in Europe, so the atheist fundamentalists are also louder.

I'm fully aware that I based this observation mostly on people I have contact with, and in at least a small part being influenced by popular culture, but I don't know of any exhaustive research or survey comparing the cultural standpoint of nontheists specifically regarding the differences between Europe and the USA.