American Beauty is hardly nihilist. It is somewhat cynical but it is about finding unexpected beauty in otherwise desolate lives. It is about every man. I don't remember where it was set because it really doesn't matter, it could be set anywhere.
Moreover, secularism and liberalism are not nihilist either. Secularism is simply the idea that one's world view should be their personal path rather than forcing their world view on society or vice versa. Liberalism is based on an optimistic view that mankind can live in freedom, brotherhood and equality and that society should proactively work toward these goals.