Let's say to give the US total "balls." You give our military unlimited support. Airstrikes, full naval uses, and shove 100,000 troops in there for any and all ground assaults. Do you think that this would solve much? If our war against the Taliban is any guide, probably not. We've been battling these guys for 14 years now and yet they're still out there. So why should it be any easier with ISIS?
You send our troops in and they go underground. And the moment you pull out, they pop out. You go back in, they go back under. You pull back out, they pop back out. All the while, they're hiding in different regions and even different countries. There's a reason why they call it whack-a-mole.
And even if you were somehow able to exterminate ISIS completely, once you pull out, some other terrorists organization will fill the void, and we're back to square one.