We are at war from that time. We are implementing war policy and footing since that time that have not been relaxed. There is a Congressional resolution still in effect that allows the POTUS to use force as he sees necessary to deal with terrorism. This is asymmetric warfare which is different to what you are inferring but it is still a state of war.
You and I are in agreement on our current state of war, but we are not under a legal state of war declare by Congress and that has legal ramifications.
Besides Iran has declared war on us. we just haven't reciprocated. But if the President asked Congress to declare War on Iran what do you think the response would be?