I responded to JohnH's comment. "According to a report recently released by the conservative CATO Institute, out of millions of refugees resettled to the United States over several decades, just 20 have committed or attempted attacks. They only managed to kill three people — all in the late 1970s before the creation of the modern screening system."  No restriction to Syria or anywhere else.  Obviously, non-resident aliens have killed many thousands of Americans with 9/11 being only the most obvious and extreme example.  The weasel word is resettled which was likely defined in fine print as having become American citizens and lived non-violently for X years.