With Secretary of State John Kerry visiting Beijing this week, China would like to see the United States express indignation over Japan’s efforts to whitewash its history from World War II. In service of that goal, Chinese diplomats have launched an unprecedented public relations blitz, arguing in dozens of op-eds and television interviews that Japan needs to be made to account for its past aggression.

On the issue of history, China’s diplomats have been convincing. Yet their message has largely fallen on deaf ears in the U.S., particularly in Congress. The lack of moral outrage in the U.S. on China’s behalf illustrates just how difficult a task the world’s most populous country faces in overcoming American fears over its growing assertiveness.

Beijing’s complaints about Japan are valid. It would be unthinkable for Chancellor Angela Merkel of Germany to downplay the Holocaust, or for a U.S. politician to describe female slaves who had been coerced into having sex with their masters as whores. Yet prominent Japanese politicians have made equivalent statements on multiple occasions in the recent past....