Hitting something is collision, being hit is comprehensive
Striking a pothole, a dropped object or debris is treated as a collision even though no other vehicle was involved, and your collision deductible applies. A rock falling from a cutting onto your car is comprehensive. The same mountain road produces both, with different deductibles and different consequences for your record.
Claiming against a road authority is difficult
Public entities have notice requirements, short deadlines and immunities that make recovery hard unless the hazard was known and unaddressed. It is worth reporting the hazard regardless, and it is not a realistic substitute for your own cover.
Tires and wheels are frequently the whole claim
A serious pothole strike damages wheels, suspension and alignment, and the total often sits just above or below a typical deductible. Knowing your deductible before deciding whether to claim is the practical step, because a marginal claim can cost more in renewal than it returns.