I think the lines sailing the Med this summer are keeping a close eye on things. From what I have heard from agents, the ships are sailing fairly 'light' and have seen many deals that would support this. Many Americans are afraid to travel over there.
I am surprised that the lines have not pulled the ships from the Med already, and would imagine they have contingency plans, whether it be to pull the ships from the Med all together or to change itineraries.
I've done the Med three times and have found the people to be very friendly, and especially enjoyed Turkey. I believe the the average person really holds nothing against Americans.