There is some truth to the idea here, but the past does matter. Doomed to repeat and all that.Whether we should have gotten involved with the shah of Iran doesn't matter now. We've got tens of thousands of very bad people who want to saw our heads off, and that needs to be addressed. A good leader is going to have to address that.
So let's say that terrorism is a fact of life now and there's no undoing a half-century of disastrous regional policy, right? We've got to combat terrorism where it has the potential to threaten American lives, etc.
Then the question has to be: what the hell are we doing in Iraq? Our adventurism there - and saber-rattling with Iran - was just a repetition of the very policy mistakes that you're saying don't matter as well as a statement of defiance to the idea that terrorism was a grievous threat to the American way of life. Our continued presence there is a continuation of these policy mistakes and only foments more anti-American feelings.
You pay attention to the past in the hopes of changing the future.