Terrorism in the United States didn't begin with ISIS, nor will it end with ISIS. Syed Rizwan Farook and Tashfeen Malik would almost certainly have taken up arms if ISIS didn't even exist. Their desire and ability to murder American citizens was unrelated to who controls the streets of Raqqa and Mosul. The upside of using ground troops may be a little less obvious. At least it was less obvious until recently. ISIS can be defeated militarily, at least temporarily. It has happened before.

Most Americans Now Support Using Ground Troops" (14 December 2015)