Most countries are fairly homogenous, which lends itself to a singular-ish mindset and culture. The US is not really one country, it's a melting pot (remember that word from social studies?) of many different cultures and ideas. That's one of the big reasons why we can't really be compared to any other country on many topics. Every locale is different, in many cases fundamentally, and that's part of the point of the Federal-State system we have.