I'm probably going to regret saying this, but from a purely analytic standpoint, Lt. Fred has a point. The trade of one American life for even a few dozen others (and that's assuming only those who die, not those who are maimed and continue living) is a light trade to the end of a bloody conflict. Is the country that soldier serves going to be thrilled? Probably not. Will the families of those rebels and soldiers who don't die be grateful? Maybe not directly, but I'll be damned if they don't realize one some level what a quick end to the war saves them in terms of loss and suffering.
Regardless of what I've said here, I still think it's best that Syria solves its own problems. Extranational intervention doesn't tend to be temporary, and nearly all modern nations have had to deal with this kind of violent revolution to get where they are today. Syria's reached that tipping point, and both needs and deserves to handle this on its own.