Complex sentence: As one of the first European riders to race in the United States, Bickers helped to introduce the sport of motocross in America by competing in the Trans-AMA motocross series in 1971 and 1972.
Split into simpler sentences: As one of the first European riders to race in the United States, Bickers helped to introduce the sport of motocross in America. He also competed in the Trans-AMA motocross series in 1971 and 1972.