Netflix said on Tuesday it added 4.3 million subscribers in the quarter that ended in December, beating its own guidance thanks to higher-than-expected interest overseas. In the United States, Netflix pulled in 1.9 million streaming customers, down from 2.3 million additions a year earlier, and forecast signing up 1.8 million more in the current quarter. Netflix believes the slowdown is “a natural progression in our large U.S. market as we grow,” Netflix said in a quarterly letter to shareholders.