That's a bit unfair, seeing as we have no idea where the picture was taken.
The biggest clues would be the narrowness of its body, the way it's kind of knife edged like that, that's a tree snake characteristic isn't it ? The scales are also a bit of a clue, they look pretty prominent, lyk individual scales, another tree-snake characteristic ? It looks venomous to me by the shape of its head. Colubrid perhaps ?
I'd say it was an american snake, but then again, for all we know it may not be a fair game at all, cld be photoshopped, or a trick question... maybe thats just my paranoia kicking in lol.
Either way i'm not a snake expert at all, just making some observations.