This is can of worms we don't want to open. As many military campaigns as we (America) have been involved in and are still involved in from the first Iraq war to drone strikes now. If all the families and survivors of what we've done over there were able to sue us in turn. We would be in a lot of trouble. What defines an act of terrorism is a matter of perspective. People in the Middle East see our bombing campaigns as terrorism. It's a double edged sword unless you think the world will allow our citizens to sue and not allow citizens of other countries to sue in kind.