US strategy in Syria should include taking out al Qaeda's'Sham' operation along with ISIL

Institute for the Study of War:

American strategy toward ISIS has misidentified the group’s center of gravity and is inadvertently strengthening Syrian al Qaeda affiliate Jabhat al Nusra. The US approach presumes that regaining Mosul in Iraq and ar Raqqa in Syria will cause ISIS to collapse, and it is not operating against Jabhat al Nusra in any meaningful way. It underestimates the resilience of both groups and the need to pressure both simultaneously to prevent Jabhat al Nusra from benefiting from ISIS losses.
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1. US strategy must operate against both ISIS and Jabhat al Nusra, simultaneously. The groups’ distinct sources of strength create different requirements for destroying each organization. Attacking the source of ISIS’s strength—its territorial caliphate—is relatively straightforward to describe, but it does not account for the fact that Jabhat al Nusra is primed to benefit from ISIS’s defeat by moving into territories from which ISIS has been cleared.

2. ISIS expansion and consolidation in Iraq and Syria has created conditions in which the group could survive losing particular cities in those countries. Recapturing cities such as Mosul and ar Raqqa will not deal the decisive blow that it likely would have in late 2014 or early 2015. ISIS can reasonably claim its caliphal capital in several major urban centers, including Fallujah, Palmyra, and Deir ez Zour. ISIS must be driven from all urban and major rural population centers in Iraq and Syria if it is to be destroyed.
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5. The US and its Western partners must alter the popular narrative that the West has abandoned the Syrian Sunni Arabs in favor of Iran, Assad, and Russia. This task will be impossible as long as the West offers the Sunni no meaningful support in the face of the Assad regime’s imminent threat to their survival as individuals and communities.
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I think it is more than a popular narrative that the US is tilting toward Iran in the fight with ISIL.   It appears to be a calculated move by the Obama administration which has also been enriching Iran under the nuclear deal.

I also question whether the Obama administration is willing to make the commitment needed to destroy both groups.