Let's see here...
On one hand, another country is in the middle of a civil war.
On the other hand, US intervention in that country's affairs by taking out their leader who held that country relatively stable for the inhabitants is the major cause in the creation of these factions', which were held in check before their "liberation" leading to their involvement in a civil war around 10 years ago and again today.
ISIS is essentially the former combined factions lumped together and coined Al Qaeda in Iraq by the former Administration. They were effectively driven out of Iraq during the "surge" after things had gone far south after "Mission Accomplished" during the "rebuilding" of the country. Now they've returned.
What should the US do? One school of thought is, we broke, we gotta fix it. Another is we've done enough damage, let the ME deal with its own problems. Between those two extremes are variations on those two themes.
The way I see it, further US involvement in the ME would simply exacerbate the problem and aid ISIS recruitment; Bin Laden's 1998 fatwa still burns in the minds of many radicalized Sunni's. One good option I see is a coalition of ME Nations such as Turkey, Saudi Arabia, Egypt, Jordan, et al, to coordinate efforts to rid the region of all the factions with Qubtism at their heart. The idea of a Caliphate rising from ISIS should be more than enough to motivate them. Now is the time for Islam to put up or shut up.
The idea of the US as part of that coalition would be absurdly counterproductive given the subject of the WIF fatwa which lead to 9/11.
Just one man's opinion, and worth about 2 cents!