But the Surge guys, the Surge worked.
It did, then we left. Just like everybody wanted.
Staying would have helped sort out this problem in the long term how, exactly? I'm genuinely curious. Even if a good argument can be made I still doubt it'd've been worth it.
Staying in Iraq would've been a massive stabilizing influence in a collapsing region where the US still has interests to look after. But obviously there came a point where the US body politic became unwilling to spend more blood/money to stabilize Iraq, which was unfortunate but predictable.
We were too headstrong from the get go in Iraq. Removal of Saddam and other dictators didn't require the full scale war we launched.
Obviously, now that we have hindsight we know that the 2003 invasion was the single biggest mistake, by far, of post-Cold War American foreign policy, but that doesn't mean that the pullout wasn't also a mistake. The past can't be changed.