We cannot do it alone as an occupation force because sooner or later we will leave. If there's not some sort of regional cooperation to go after ISIS, any action on our part will be both limited and fruitless in the long run. How many more American soldiers do we want to see coming home in body-bags until we get this through our heads? After Vietnam, Iraq, and Afghanistan, you'd think we would have learned our lesson, but the unfortunate reality is that too many haven't.
Unless there's some sort of regional cooperation, the only real recourse we have is to continue our attacks by air to diminish ISIS' ability to occupy the region, and this will have to be extended into Syria as well, imo. Yes, we can protect our own people in Iraq with some additional troops for protection, and I have no problem with that as a short-term action.
Turkey and the Saudis have played a major role in the creation of ISIS, so I thinks it's time that we and the NATO powers lean heavily on the former at the least. It's "put-up or shut-up time" for them, as far as I'm concerned, and if they aren't willing to do either, then we should reconsider our commitment to both of them.