New Starbucks CEO Brian Niccol will focus on improving the chain's U.S. business in his first 100 days on the job before he moves to fix its issues abroad, according to an open letter published on Tuesday.The coffee giant named Niccol as chief executive in August, in conjunction with the company's ouster of then-CEO Laxman Narasimhan. The leadership shakeup followed several quarters of slumping sales for Starbucks as demand for its drinks declined, particularly in the U.S. and China.Niccol's official first ...