ISIS is certainly a problem in the mideast but many analysts don't think they are much of a threat here - certainly not enough to commit U.S. warfighters. Khorasan apparently has a different mission, collecting western wanna be jihadists with passports. That's bad....
http://www.washingtonpost.com/news/morning-mix/wp/2014/09/22/the-elusive-figure-u-s-officials-fear-as-much-as-the-islamic-state/?tid=hp_mm&hpid=z3
http://www.washingtonpost.com/news/morning-mix/wp/2014/09/22/the-elusive-figure-u-s-officials-fear-as-much-as-the-islamic-state/?tid=hp_mm&hpid=z3