More than 10,000 foreign fighters are battling alongside ISIS and "dozens" of American citizens could be holed up with various extremists groups at any time, according to U.S. officials. The threat posed by American jihadists, such as Douglas McCain, is alarming to the U.S. government, which has devoted significant resources to understanding the risk homegrown extremists pose. Some say that American jihadists are a direct threat to the U.S., as trained militants could come home and set off explosive devices in U.S. cities. Others, however, believe it's more likely that they'd return to America discouraged and disillusioned, not dangerous.
