Food from American supermarkets is generally so well preserved and packaged that it lasts a Very Long Time.
It's actually pretty difficult to buy fresh produce that you can cook with; it's much easier to buy something pre-prepared or microwaveable instead. Once you do find basic ingredients, you often realise that it's cheaper to eat out in a low-key establishment.
This could explain why so few New York apartments have functional kitchens.
One supermarket chain is making a killing at the moment. Wholefoods is very successfully filling the gap, and sells beautifully fresh food alongside organic and luxury pre-packaged items. Every branch is always busy, so they're clearly on to something. This also seems to grant them licence to charge about twice the price of everyone else for the same items. Ah well.
It's also interesting to note that not everything you buy from a supermarket actually has a "use by" date. Maybe "food" here really does Live Forever.