Did you get the alignment done at a shop, or just adjusted it yourself by eye? You could have too much toe in on the steering, where the wheels point in a bit too much. this would cause the front end to be kinda twitchy like that.
When going in reverse, is it also sensitive, or less so than before? Also, did you get new tires at the same time? Some tires like to grab ruts & cracks in the road.