Foodie-ism, as it turns out, is subject to the rules that traditionally govern other forms of geekdom: there is an obsession with origin, a need to discover, and a need to own, and a tendency to use those three things to assert superiority over others. But there's more than that. It's something rooted in the American experience (and hell, quite possibly the experience of many liberal democracies of the West, since now they all have foodie assholes wearing weird backpacks).
American food traditions, like Americans themselves, are messy, complicated, and mostly just came from other places. We as Americans are proud mongrels and so is our food. There is little by way of purity or simplicity. Unlike the use of France's appellation d'origine contrôlée (AOC) and Italy's denominazione di origine controllata (DOC), which hold things in a specific region to a set of clear and specific standards, we do no such thing in America, outside of a handful of products, like making sure Vidalia onions are grown close to Vidalia, GA, recognizing bourbon as a "distinctive product of the United States" in a 1964 Congressional resolution, or ensuring that "100% Florida orange juice" does not contain any Sunny D or purple stuff from other citrus-growing states.