Check MRI. Cx spine; there may be compression of the spinal cord before surgery or in postoperative period.

Generally speaking, surgery to the cervical cord does not cause ataxia. Without knowledge of your full medical history, it is hard to reason why you are ataxic. I would call the surgeon's office and get a reply from him/her.

May be related to spinal cord injury. Please consult with a neurologist.

You need to see a neurologist and need to have MRI of the neck ,if you did not have one after the surgery

It’s difficult to give a complete answer without more information. Sometimes after surgery ones balance can worsen. But most find that they improve over time. Are you saying that your balance just now worsened? You would really need to be seen by an expert to receive a thorough assessment before informative advice could be offered.