The American artist known for his works in modern abstract art is Jackson Pollock. He is renowned for his pioneering style of drip painting, which involves pouring and splattering paint onto canvases, thereby creating dynamic and expressive compositions. Pollock's work is often associated with the Abstract Expressionism movement, emphasizing spontaneity and emotion. His innovative techniques and unique approach to art revolutionized modern painting, challenging traditional artistic conventions and inspiring future generations of artists.