Another reason why Japanese do not hold grudge against Americans is that Most of the teachers influenced by the communist power teach ‘masochistic history view’ at school in Japan.
The same is true in China and Korea about the education controlling the national feeling.
They hold grudge against Japan because education teaches the people to hold grudge against Japan.
As is seen in Nanjing massacre, China teaches their people about what did not happen as if it had happened. Korea, besides that, teaches their people about what good deeds Japan did as if it had never happened.
In Korea, you get criticized if you make any pro-Japan statements. You are not allowed to make any pro-Japan statements even if it is based on facts and truth. On the other hand, you get praised if you make anti-Japan statements even if it is based on lies.
When we see these situations, we will be able to understand that the national feeling is not created by history but by education or mass media.