Why do the japanese know little about their families occupation?

Well, there are many reasons, but the main reason is that their government does not want them to know their families past. They want their people to start with a clean slate

to protect the united states' role as a world leader, president truman wanted to prevent the soviet union from spreading communism beyond its post-world war ii boundaries. he declared that the united states must assist any nations struggling to prevent a communist takeover.