It's crazy how different alcohol is treated, culturally and legally, in America compared to many European countries that don't have a legal minimum age. They can make it work well, which undermines some of the arguments Americans have against changing the legal drinking age out of a fear that it will drive some sort of cultural collapse.
I love your prospective. Obviously America is very different culturally than Europe, but I honestly don't know if much would change if it went back down to 18.