According to the Insurance Information Institute’s table of Automobile Financial Responsibility Laws by State, 49 out of all 50 states, as well as the District of Columbia, require you to have some sort of liability coverage for all vehicles on the road, including RVs. The only exception to this rule is the state of New Hampshire, which has no mandatory insurance law, and only requires financial responsibility from the person at fault in a car accident.
Comprehensive car insurance covers damages from an "act of God," or events that are not caused by a car driving into something else. An "act of God" can include things like damage from a heavy tree branch falling on your car. Since you have no control over when or why a tree branch would fall on your car, this kind of accident would be covered under your comprehensive policy.
When judging coverage and benefits, we singled out RV insurance carriers that offered extensive and flexible coverage options. To be considered for our list, companies had to provide all the traditional insurance protection, as well as a healthy amount of RV-specific options. Most RV insurers offer liability, personal injury protection (PIP), collision, underinsured or uninsured motorist, and comprehensive coverage. Other types, such as full-timer and Mexico coverage, vary in availability from company to company.