Not sure why you'd doubt that. We have the best weapons of war by far. Iraq's government was considered a regional powerhouse, and the Coalition took it down in a month. Syria is not only not that, but has been embroiled in a civil war for a year. They'd crumple like paper to a US or NATO intervention.
He's not talking about the initial invasion, he's talking about the power vaccuum. He doesn't think NATO has the ability to keep insurgencies down, which, admittedly, we don't have a good track record with recently.
Of course, the intervention would be better placed early on, before the Extremists get their hands on it, but we wouldn't have justification. It's a catch-22. Mostly because the U.S government is more concerned about their world power rather than actually helping people, but all governments are and I doubt that's going to change.
I think keeping our help on the downlow would possibly be better. Assassinate well-chosen targets and help the resistance along without actually putting many American boots down. That way we could influence their government without much backlash here, letting us deal better with the backlash over there.
Really though the best thing to do would be education, for everyone. If we can educate a generation the Extremists will have a very hard time indeed taking the territory back. It's that first generation that's the hard part, when their parents are still more crazy than not.
Unfortunately, look at libya today. Miltias running all over the place. People don't want that.
This happens every time there's a civil war, IIRC. Look at America right after the Revolution. Every state for themselves.
If we were smart, we'd start directing Libyan government along the same thought patterns that led to the modern Union. We shouldn't try to set them up like we are right off the get go, but we can give them a swift kick down the road.