The Sunni Islamist surge may also be essential to inflicting a full-blown strategic defeat on Iran. Once the regime is toppled, Assad and his minions will likely retreat to northwestern Syria, where non-Sunnis are (barely) a majority. This could result in a rump state in the Alawite heartland, secured by chemical weapons and Iranian-supplied resources and arms. For all of their faults, Sunni Islamists hell-bent (or heaven-bent) on purging the country of Iranian influence can be counted on to reject a "no victor, no vanquished" settlement like the 1989 Taif Accord, which brought Lebanon's civil war to a halt but institutionalized its political fragmentation and loss of sovereignty.
While there is sure to be regional spillover, it will cut mainly against Tehran. There will be tough times ahead for Lebanon, but ultimately the Assad regime's death throes can only work against the Shiite Hezbollah movement. Iraq's ruling Shiite leadership, hitherto sycophantic where Iranian interests are concerned, may find it necessary to distance itself from Supreme Leader Ayatollah Ali Khamenei's more unpopular Arab clients. With its own restive Sunni minority, Iran itself could be severely rattled by sectarian blowback.
Of course, Syrian Islamists are no friends of the United States -- merely the enemies of one of its enemies. Indeed, their long-term aspirations are arguably more reprehensible than those of the mullahs in Tehran -- Shiites, after all, aren't obsessed with converting others their faith. Syrians have also been prominent in the leadership of al Qaeda, easily recognizable by the surname al-Suri in their noms de guerre: Notable examples include Abu Musab al-Suri, a major al Qaeda ideologue; Ghazawan al-Suri, the leader of al Qaeda in Mosul captured in 2007; Abu Zaid al-Suri, a deputy leader of al Qaeda in the Iraqi town of Rawah, captured in 2006; Abu Layla al-Suri, the leader of al Qaeda in Diyala, killed in 2008.
For the foreseeable future, however, Iran constitutes a far greater and more immediate threat to U.S. national interests. Whatever misfortunes Sunni Islamists may visit upon the Syrian people, any government they form will be strategically preferable to the Assad regime, for three reasons: A new government in Damascus will find continuing the alliance with Tehran unthinkable, it won't have to distract Syrians from its minority status with foreign policy adventurism like the ancien régime, and it will be flush with petrodollars from Arab Gulf states (relatively) friendly to Washington.
So long as Syrian jihadis are committed to fighting Iran and its Arab proxies, we should quietly root for them -- while keeping our distance from a conflict that is going to get very ugly before the smoke clears. There will be plenty of time to tame the beast after Iran's regional hegemonic ambitions have gone down in flames.