I've been to the US a couple of times and most restaurants I visited did not have any parking spots at all. I have also seen plenty of food-carts operated by a single person, comparable to the Japanese mini-restaurants described here.
It's not federal. It'll come down to the state and municipality. If you were in a denser city, it's likely they didn't have that requirement. Lots of New York City doesn't have this kind of requirement, but you may see that if you were in a more suburban area
I'm guessing you stayed in a major city and didn't drive anywhere outside of it? If you flew in and didn't have a rental car, odds are your itinerary was biased towards places that didn't need a car?
