I think we could've played "hands-off" in 1967 and 1973 and allowed Israel to have finished-off some arab armies. We were worried what the Russkies might have done, I know. But I don't think they would've. The implication of your question is sound: no matter what we did or did not do, we'd probably be approximately where we are. We are too civilized; we pull punches. No one should have to go to war pulling punches. It's like a bad dream. Our opponents NEVER pull punches. Never. This asymmetrical warfare is tiresome.
What can we do, we are not the Roman Empire. I am glad of it, but it does make it harder to have our way in the world.