One of the highlights of the state dinner was a performance by Lang Lang, a Chinese pianist who has been a sensation in music circles. Mr. Lang played a duet with the American jazz pianist Herbie Hancock, then a haunting traditional Chinese melody called “My Motherland.” In China, it turns out, “My Motherland” is better known as the theme from the film “Battle on Shangganling Mountain,” a 1956 Chinese classic about a Korean War battle in which a vastly outnumbered band of Chinese soldiers held off American and United Nations forces for 42 days. If, in retrospect, “My Motherland” might...