It's not a question of that, given the Hatian government explicitly asked for help from the international community and not just the US. The draft the US is drawing up for the UNSC charter is for a rapid response force which, coupled with last weeks announcement that it was too early to discuss any kind of "US security presence," would suggest that the intent is for an international UN peacekeeping force which would presumably, be made up of partly or wholly of other member state peacekeepers.
Also, this isn't a civil war, at least not in the proper sense, for the simple reason that there doesn't appear to be a coalition in place between the various "criminal gang" factions that are opposing the government. It more closely resembles the war that the Mexican government is fighting with the cartels, which would be a strong indication that any kind of involvement by the US would be at best unnecessary.