Why are Americans less open-minded and way more conservative than Europeans?

I live in the Netherlands and it is so liberating here I love it. I know American people and it seems like Americans have much more conservative views and think things are so "morally wrong", stuff that wouldn't even be given a second thought here or in the rest of Western Europe. Things like different kinds of relationships that are not the norm, , nudity, drinking age, marijuana use. Even the acceptance of evolution. Anyone who has open minded views should come here and see Amsterdam because its the best city ever.