A lot of foreign flag carriers get government subsidies that translate to excellent catering and service onboard. This works in that nation's favor because tourists will have a positive impression of their airline and therefore the country itself. For example, I like to fly ANA because their service is wonderful.
On the other hand, the reregulation of the US air industry that happened in the 1970s has created a race to the bottom of chasing ever cheaper, unbundled fares. US carriers aren't thinking of national prestige, all they care about are their bottom lines.