AP Explains: How a single Trump sentence enraged South Korea

U.S. President Donald Trump's apparently offhand comment after meeting with Chinese leader Xi Jinping — that "Korea actually used to be a part of China" — has enraged many South Koreans. The historically inaccurate sentence from a Wall Street Journal interview bumps up against a raft of historical and political sensitivities in a country where many have long feared Chinese designs on the Korean Peninsula. It also feeds neatly into longstanding worries about Seoul's shrinking role in deal...