While I agree with you on other points, I take issue with this. American grocery stores are a real treat when visiting. Produce is colorful, plentiful, and delicious thanks to American embrace of GMO's and subsidies for farmers. Raw ingredients such as flour are available in huge variety (try finding something as simple as peanut oil at your local Lidl). Even the quality of "junk" food is comparably fantastic, as you won't find a frozen pizza like DiGiorno anywhere else. This is all before you visit a Whole Foods, which takes quality and variety to a point which organic supermarkets elsewhere in the world can't compare.
Europe, on the other hand, is so obsessed with the discount model, so disinterested in variety, and so opposed to GMO's, that their supermarkets are downright frustrating. Yes, the meat, cheese, and chocolate is great, but it stops there.