Complex sentence: He is the first Korean driver to have raced in the American Open Wheel Series (Pro Mazda, USF2000), one of the first Korean drivers to have participated in any race held in the US.
Split into simpler sentences: He is the first Korean driver to have raced in the American Open Wheel Series (Pro Mazda, USF2000). One of the first Korean drivers to have participated in any race held in the US.