Question is why did it snap. If it wasnt crossthreaded then it should be somewhat easier to get out. If you pull the hatch cover and can see the end of the bolt you could be able to just grab the end with some pliers or vice grips and turn it out.
If its crossthreaded then you're probably into a drill and extract.

 

Recently moved and got new tags. Installing the screw back in I must have cross threaded it which is weird because I was really trying to be careful not to do that. It was going in smoothly until about halfway down when it started to bind a little. I gave it just a hair of pressure and the screw snapped. Still have not had any luck getting it out. Been busy, going to give it another shot this weekend.