Seven American troops and four Afghans died in a Black Hawk helicopter crash on Thursday in southern Afghanistan, the NATO military coalition said. The Taliban claimed their fighters shot down the aircraft. The crash marked another deadly day for the U.S. in Afghanistan, less than a week after six American service members were gunned down, apparently by two members of the Afghan security forces they were training to take over the fight against the insurgency as international combat troops prepare to exit the country by the end of 2014.