NEW YORK — This year showed how sheltered the U.S. economy is from geopolitical and health crises around the world. The global economy sputtered, but the U.S. powered ahead. Employers are finally hiring enough to lower unemployment. A plunge in gas prices and a rising stock market has Americans feeling richer and spending a bit more. Those are some of the top business stories of 2014, as chosen by business editors at The Associated Press. Others include massive product disasters: A string of auto recalls …