What's a Superpower to Do?
Suppose that you've been spending more on your military for twenty years than your ten or twenty possible rivals combined, most of whom are your allies or at least not actively hostile. This is the problem Rome faced around the start of the first millenium BC, and the US faces today. Rome concentrated its energies on tearing itself apart as rival oligarchs fought for power.
Being the world's policeman turns out to be very expensive. Forcible reshaping of the world in your image is also pretty difficult. We've tried both, with limited, but hardly zero success. An extremely expensive war and reconstruction turned Germany and Japan into functioning democracies hard to tell from their older counterparts in the West. Another costly effort worked in South Korea.
Vietnam, Iraq, and Afghanistan are all notable but hardly total failures - though in Vietnam we had to lose badly to get an approximation of what we wanted all along. Attempts to intervene in Libya and serve as a cheerleader in Tunisia, Egypt, and Syria have been miserable failures.
Syria is practically a poster boy for all the ways that meddling can go wrong. Faced with a purely indigenous popular revolt against a vicious tyrant, it's hard not to sympathize with rebels. Unfortunately, the man behind the curtain, AKA Israel, was fairly happy with the tyrant, and even happier with a Syria tearing itself apart. We chose, I think, one of the worst options, publically siding with the rebels but giving them only token and ineffective aid. Naturally this angered everybody involved and probably multiplied the bloodshed.
Suppose we had intervened decisively and early to crush Assad. What would we wind up owning, besides the satisfaction of sending one more jerk to oblivion? That was the puzzle nobody could give a happy answer to. More civil war, rule by Shiites sympathetic to Iran, or yet another failed state?
From the 1000 mile high perspective, the turmoil in the Islamic world is just part of the collision of that world with modernity. In the meantime, the people there, and the rest of us, will continue to live in interesting times.