Gaucho100K is certainly correct. i think it is quite natural to gravitate towards chains when discussing the US food scene, just because there are so many of them. In absolute terms I think there are probably more fine restaurants in the US than in any other country. Even if fewer of them, proportionately, are the absolute finest in the world there are large numbers that do qualify for such a designation. Other threads can list them and I have candidates in many cities.
At this moment I'm in Coral Gables, Florida. Dinner at Pascals on Ponce was truly excellent and the dum sum served as it is in Hong Kong at Tropical Chinese(they don't count the plates but mark them on a paper) is a place I go every time I manage to be here on a Sunday. That is an experience worthy of approval even in HK.
One of the less pleasing points often mentioned in this thread is the typical quality of American eateries. On average the US food is absurdly plentiful but poorly prepared, though it is very, very cheap. The very title of this thread implies, to me at least, that we're discussing the average, not the best.
Maybe the thread needs some fine-tuning. It has been very enjoyable to read so far without absolute clarity in the definition .