In Japan, meals at home are for eating, because your stomach is vacant. At an American’s dinner, there is food, decorations on the table and tableware, and music to produce a fun atmosphere. It is a time for maintaining rich human relationships. Therefore, the meal is as long as 40 minutes.
However, they toe the line of politeness to the point of frequently not telling the truth, even though it's expected that you get the gist. I guess it's because people there have an aching sense of what failure means to them. Meanwhile, in the U.S., you can get away with being a proud fuck up, making it easier to speak plainly about your faults. Sometimes it's seen as valid justification not to excel since there is a stronger sense of individual identity here.