One of the world’s biggest clothing buyers, the United States government spends more than $1.5 billion a year at factories overseas, acquiring everything from the royal blue shirts worn by airport security workers to the olive button-downs required for forest rangers and the camouflage pants sold to troops on military bases. But even though the Obama administration has called on Western buyers to use their purchasing power to push for improved industry working conditions after several workplace disasters over the last 14 months, the American government has done little to adjust its own shopping habits...