Starbucks has a problem: Sales at U.S. stores have fallen sharply and now the company is looking to China, its second biggest market, to boost its revenue. But as WSJ’s Spencer Jakab explains, increased competition there is making that a tall order.  Further Reading: -Starbucks Is Running Out of Americans to Drink Its Expensive Coffee  -The Furious Race for the Future of Coffee Further Listening: -The Underdog Coffee Bean That’s Making a Comeback  Learn more about your ad choices. Visit megaphone.fm/adchoices