One thing I would do in conjunction with gently bending it back into shape is find something round and sturdy, like a ratchet handle or socket wrench extension, that exactly matches the radius of the nominally intact dropout. Use this as a mandrel in the U of the distorted dropout while you are persuading it back into shape. It would also be good to constrain the bottom of the U laterally with a C-clamp or adjustable wrench, so that it stays flat while you reshape it longitudinally. You probably need a buddy to lend an extra pair of hands, in order to do everything simultaneously.