In my (admittedly limited) experience, American restaurants, steakhouses etc serve high-quality food, well-cooked and affordable, while US supermarkets seem to supply food which is over-processed, bland and relatively expensive. Almost exactly the reverse of the situation in the UK. Is it in fact true that Americans eat out or utilise take-away more often than Brits do?
Our aristocracy are almost universally of French extraction and have always eaten French cuisine, so 'native' British cooking is invariably 'peasant' cooking. This explains the reliance on root vegetables, cheap cuts and offal and the general lack of seasoning. It also explains such oddities as unsalted butter (popular in the North) and our wide variety of regional cheeses (Britain currently produces over 700 indiviually-recognised varieties).
In the matter of portion size, I have noticed that Americans are not averse to leaving uneaten food on their plates. This is in direct opposition to the British conviction that failure to 'clear your plate' is not only bad manners, but unforgivable waste. Before WW2, middle-class children were urged to 'leave something for Mr Manners' as an indication of not being greedy. But the food rationing of the 1940s and 1950s gave rise to a 'clear your plate' imperative that is only just beginning to fade.