Since ISIS is per se a threat to America and America’s interests, we have every right to go in and wipe them out. Again, as long as we have the will, the focus, and superior might, we will crush them as we have in the past. Under Trump we have all those things. Still not sure what you’re puzzled about.
We crushed them last time with the assistance of 60,000 Kurdish fighters backed up with a few hundred U.S. soldiers in support. That's no longer a solution so if we have to go in against an Isis caliphate again it's with thousands of U.S. troops.