(1) Historical factors have combined to produce a fiercely nationalistic population on both sides of the DMZ.
Multiple kingdoms existed on the Korean Peninsula from the first century. (So one might say Korea is five times as old as the United States.) From 936 to 1910, Korea constituted a single state, embracing the whole peninsula, populated by a relatively homogeneous people. The division of the last 82 years is anomalous. Koreans feel a deep sense of national historical victimization—especially by Japan and the U.S.—but have suffered many invasions in their long past. The Jurchens (from 10th century), Mongols (1231), Japanese (1592-98), Manchus (1627), and Japanese again in the twentieth century, and then the Americans. Most Koreans of my acquaintance express themselves passionately about this legacy of abuse, and commitment to eventual reunification following the 1945 division they properly blame mostly on the U.S. You don’t want to provoke Koreans with schoolyard bully talk.
(2) Korean culture has derived much from Chinese culture for 2000 years, and China has influence. But China doesn’t control Korea.
While Korean culture is unique, it has (like Japanese and Vietnamese cultures) been deeply influenced by China and Confucianism in particular. For a thousand years, Korea was one of China’s tributaries, enjoying the right to trade in China in return for its kings’ formal acceptance of vassal status. Koreans have traditionally viewed China as…