If the oil there dried up mañana- we'd pack up all of our shit in a week and never go back regardless of isis, or any other bag of asses.
While we don't have a real military presence in Africa where terrible things happen every minute, rest assured if they discover resources we want, we'll "do the right thing" as a nation and allow major corporations to exploit these folks for a while. All under the watch of the US Armed Forces.
Why do you say it as if it is a bad thing? Or maybe you don't. Remember we didn't make the nukes, we made the nukes fly. Iran and Pakistan have nukes, and so does Israel.
We have a need to be there, to keep Iran from rolling over Saud, and stopping, not our oil, we have ours.
This also about the trade, and Jihad was a problem long before oil was discovered. We cleaned out the Med of the Islamic Shipping Tax, so we own it. We protect it, oil or not.
So, no, this is not it. Africa is just land mass, not the center of all sea routes between Europe and Asia.