The best course of action in the Middle-East has always been and continues to be non-interventionism combined with immigration restrictions – in other words, the approach of Japan.
The fact of the matter is that Islamic State in the Middle-East is not a significant much less existential threat to the US. And despite the schizophrenic paranoia of the Jewish community, it isn’t a threat to Israel either. The demographic trends in Europe, on the other hand, poses a legitimate threat to global stability but that's a story for another day.
What ISIS poses a real, indeed existential, threat to are the Shia of Syria (Iraq where the Shia are a majority is a different matter). The natural course of non-interventionism in the ME is that ISIS, which will probably emerge as the de-facto leader of the Sunni Arab world, will attempt to exterminate / forcibly convert the Shia, starting with the Shia in Syria.
Since Iran isn’t going to sit by and watch its Shia wiped out in Syria, whether via genocide or conversion to Sunnism makes no difference to them, the situation in the Middle-East will naturally evolve into possibly an all-out sectarian war, a war that has been in the making for over a thousand years, in fact.
And the only reasonable response the rest of the world can muster in such a scenario is to close its doors to the Middle-East and let its people sort out their own problems. The Middle-East is inherently a ticking time bomb anyway because its borders are mostly artificial – Sunni and Shia, Arab and Kurd and Persian will never be able to live together peacefully within the same borders.
If they don’t exterminate each other, the denouement of such a war will be that the continent with shatter along ethnic and religious lines – the Sunni and Shia, the Arabs and Kurds etc will all form their own ethno-religious states. And the regions groups all going their separate ways is the only long-lasting solution to that region's problems.
