Yet so far no U.S. citizen involved in fighting or supporting the Nusra Front or ISIS has been charged with plotting to conduct an attack inside the United States despite the fact the war in Syria is now in its fourth year and the war in Iraq is in its 11th year. Indeed, some Americans who have traveled to Syria have ended up dead apparently because they have no combat experience to speak of; for instance, Nicole Mansfield from Flint, Michigan, was killed in Syria last year by forces loyal to the Syrian dictator Bashar al-Assad.

Further, ISIS’ predecessor, al Qaeda in Iraq, never tried to conduct an attack on the American homeland, although it did bomb three American hotels in Jordan in 2005.

And it’s also worth noting that in none of the successful terrorist attacks in the States since 9/11, such as the Boston Marathon bombings last year or Maj. Nidal Hasan’s massacre at Fort Hood, Texas, in 2009, did any of the convicted or alleged perpetrators receive training overseas.

Returning foreign fighters from the Syrian conflict pose a far greater threat to Europe, which has contributed a much larger number of foreign fighters to the conflict than the United States, including an estimated 700 from France, 450 from the United Kingdom and 270 from Germany.