Yahoo News explains: Why is the U.S. in a trade war with China?

On Monday, President Trump announced tariffs on $200 billion dollars worth of Chinese goods. It’s the second round of tariffs on Chinese goods this year. The Chinese have likewise imposed tariffs on $50 billion in U.S goods this year. Both sides have threatened to impose even more tariffs. Why is the U.S. in a trade war with China? Yahoo News explains.