Quote from the recent N20 North Americans NOR:

"Competitor’s Insurance:
Each competitor must show proof of Liability Insurance with a minimum coverage in the amount of $300,000 USD that is valid while sailing in the United States. Competitors with foreign issued insurance policies must show proof that their insurance is valid while competing in the United States. Competitor’s proof of insurance and coverage must be provided at registration. . Anyone chartering a boat from Performance Catamarans, Inc. or a private individual must purchase Borrowed Boat and Liability Insurance at registration."

Some basic insurance comes with being a member of US Sailing? or is that for race organizers?