Those large stores are where most people buy food. The margins for food in them are very low, but they make it up by volume. Smaller stores cannot compete on price or selection, and so even if there is a small store close Americans will make regular trips to the large store that has everything at a low price for most food. There isn't much room for the small stores anymore.
There are pros and cons to the above. Do not claim what you are used to is better: it is different, not better or worse. Odds are you have not spent enough time using both to make a real claim. even if you have, odds are your stage of life is different enough that you cannot compare.