WW2 was officially in progress for 27 months before we went in. We had no consensus until we were attacked.
We have even less will to fight now.
Had we not been attacked, we might have left England hanging out to dry. And now, we might very well leave Israel, unless something extraordinary---and very tragic for us---comes to pass.
We will not attack Iran until there is a significant event that would justify such an attack. Unfortunately, this means that when we finally do what needs to be done, the consequences for us will be much more serious.