You are correct that for tax years 2018-2025, casualty losses are not tax deductible unless associated with a federally declared disaster, like a hurricane, flood, or wildfire. There are no federal deductions for losses of this type on a personal vehicle.
You may still enter the loss in the casualty section, because some states may allow the deduction, and your federal entry will flow to your state return. But you will have to answer that it was not caused by a federal disaster. The amount of the casualty loss is the loss in value of the property. The repair cost to restore the property to as-was condition can be used as the loss in value. Or you need an appraisal. For 2004 used car, you can determine the as-was value from Kelly Blue Book, Edmunds, or another reliable car valuation site. If the car has no value after the accident, then the loss in value is equal to its original as-was value.
