No, we have not declared war on any country since WWII. Notice how incomplete each military action since then has been. Congress has given an “authorization of military action” on all conflicts since then, because it gives them a way out. If it starts getting tough they can back out without a formal surrender. If they declared war they would be all in. You either definitely win or you definitely lose. They don’t have the balls for that.
A declaration of war always involves a treaty at the end or a formal surrender at the conclusion. These military “engagements” have no definite conclusion. In Vietnam we just withdrew. Gulf War I the UN drew up a ceasefire, etc.
Yep. we should have declared war on Iran on 9/11.