My reply, however, was to point out that those who argue that the "laws, customs, and cultural traditions in western Europe are much more rational/intelligent/better/whatever than those in America" are actually ignorant of the actual history of Western Europe.

More specifically, lvh's comment about "As a (western) European" is an incorrect generalization. There are western European countries where it's impossible to buy alcohol from convenience store. I believe that your response should not have been to bring up any special history of the US - thus inviting a pissing war - but instead highlight the parochialism in lvh's observation.