How much does Islamic State threaten U.S.?

by Greg Miller and Juliet Eilperin

Intelligence agencies remain uncertain about the scope of the danger that the militant group poses to the United States.
...
[President Obama is the] commander in chief who presided over the creation of a counter­terrorism doctrine in which U.S. strikes are supposed to be contemplated only in cases­ of imminent threat of violent attack. Faced with a terrorist group that is expanding faster than U.S. spy agencies can chart it, the “imminent” threshold appears to have been set aside.

So we're bypassing Congress and the American people and going to war because polls show people at home here are fearful, now that they've watched (or more likely, heard of) the beheading videos?

Who exactly is going along with this, and for how long?