Al Qaeda captured Mosul – so what is the matter for us?
The matter is that at this point there will be some kind if covert or not covert US involvement.
In Mosul Al Qaeda captured also US (Iraq lent) Blackrock helicopter and modern US weaponry, 48 Turkish Embassy hostages, over US$400 million and threatening the Iraqis oil sites (and oil prices). Practically they are forming the Arab Caliphate of the wildest dreams.
So there will be intervention in one form or another.