Differential Unit problems of the 2005 Subaru Impreza

I was travailing 40-45 mph on a 2 lane road in my 2005 Subaru wrx sti. I came out of a small s curve and went over a rough patch of road, and the tail end of the car started sliding out to the right, the next thing I knew I had ran into the bank and I was facing traffic, I hit the bank at least 40 mph, there was a car in front of me and one behind me, and one coming in the other lane of traffic. It felt like the tail of the car had tightened up and sent power to the rear wheels and kept me sliding until right before I hit the bank it swung the car around like it had sent all power to the front witch in turn put me into the bank. Nothing worked. No air bags deployed. The seat belts did not restrain me, I hit my head on the side window because none of the safety features worked on the car I sustained injuries including: whip lash, severe headaches and I may have a fractured a vertebra in my back. Contacted Subaru of America and they blew me off saying that there was no defects in the car, and that they waited till the government told them to fix something before they would fix any problems.