The airline transport certificated pilot was conducting a 14 CFR Part 135 on-demand passenger flight in a tailwheel-equipped airplane. The pilot said he flew over the airstrip, and the wind sock indicated a strong right crosswind. As the airplane slowed during the landing roll, he said he lost rudder authority, and the airplane ground-looped to the right. He said the left wing received structural damage when it struck the runway following the collapse of the main landing gear. The pilot said there were no known mechanical anomalies with the airplane prior to the accident.