The argument goes something like this: “This regime in Syria serves as the main forward operating base of the Iranian regime in the heart of the Arab world. It has supported Palestinian terrorist groups and funneled arms of all kinds, including tens of thousands of rockets, to Hezbollah in Lebanon. It remains a committed enemy of Israel.” That was Senator John McCain, writing in the The New Republic.

Topple Assad, the theory goes, and Iran loses an ally, Israel an enemy and Hezbollah a critical patron. So far, so reasonable, even if the connection to U.S. security is tenuous.

But all of the benefits that supposedly accrue from toppling Assad only occur if Syria is able to reconstitute itself into a stable, secure government that rejects Iranian goals and prevents al-Qaeda cells from spawning in its midst. What are the odds of that?

At the moment, they appear bleak. No international peacekeeping force, not even a regional one, is poised to enter Syria to police it when and if the Assad regime crumbles. As the U.S. learned in Iraq, it takes well over 100,000 troops and the cooperation of vital sections of the population to adequately pacify a country cleaved by civil war — and even then, violence and disorder remain potent forces.

It’s always possible that the various militia groups waging war against Assad will decide to lay down their arms and cooperate to form a government that can successfully police all of Syria, but that appears to be a long shot. What appears more likely to happen is that U.S. arms and interference will accelerate Syria’s collapse into a failed state. In such an environment, there will not only be ample opportunities for Iran to preserve, if not extend, its influence, but there will be newfound threats to U.S. security including the establishment of additional safe havens for al-Qaeda-aligned jihadist groups. That’s a net-negative for U.S. strategic interests.