Since the wreck was not your fault, the other person's insurance company is responsible to make you "whole" again. They must pay to repair or replace any items damaged or pay you the fair market value of any item not repaired or replaced. A request to have the hitch inspected by a qualified inspector is not unreasonable. They may very well claim their inspector is qualified, and he or she may very well be qualified. You can ask what credentials make the inspector qualified. You can also hire an independent inspector yourself and demand payment.
If you not yet have "soft tissue" injury from the forces of the wreck, you may start to feel pains, and you are due compensation from the insurance company for your pain and suffering. Also, some states allow for payment for diminished value- that is the amount your vehicles are now worth having been damaged and repaired as opposed to never have been damaged.