I don't think that strategy alone works long-term. The Romans tried it in Germany.
Instead of a purely static defense, you need punitive retaliations to back it up.
Put up the border defenses in Iraq - after blasting Syria back to the stone age, and creating enough destruction Iran to prevent futher development of their nuclear program and allow any dissidents to drive out the ayatollahs and take over.
But don't bother to send in American troops or dollars to help put Syria back together again.
Let the Syrians rot until they evolve into humans.
Let the Iranian revolutionaries remove the current leaders and use Iran petroleum dollars to rebuild the destroyed infrastructure and, if they wish, provide them with financial and technical assistance.
The foregoing is the only solution to the immediate problem.
Then we can switch focus to the Wahhabists in Saudi Arabia and deal with them next.
Let the Syrians rot until they evolve into humans.
"Let the Iranian revolutionaries remove the current leaders and use Iran petroleum dollars to rebuild the destroyed infrastructure and, if they wish, provide them with financial and technical assistance.
The foregoing is the only solution to the immediate problem.
Then we can switch focus to the Wahhabists in Saudi Arabia and deal with them next."
Let me focus part of the problem which is oil. WHEN we decide to move away from foreign oil, we can do these things. Until then, Iran is going to get away with whatever they want and we're going to let them. Syria is a different matter and one that can be handled almost at will. Right now, neither countries are afraid of us. We did nothing to them for 30 years while they attacked us by proxy.