Technically we are still at war with North Korea but it is defined as a police action. No war has been declared by Congress and I doubt it ever will be unless maybe we suffer a Nuclear attack and then only if Republicans controls both Houses.
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.