Q: On interstate, car severely vibrated and pulled to left

While I was driving on the interstate, my car began to severely shake and vibrate. At the same time it was pulling to the left and steering had become very difficult; plus, there was some loss of control. I managed to get to the shoulder of the road and took a look. The cross beam was rusted through. On the left driver’s side the control arm had broken free. I had the car towed to the nearest dealership (Chevrolet). Previously I had them check for this same problem and had been told there was no issue or recall for my car. Before I proceed with any more repairs, what do you suggest is needed to correct these problems?