Complex sentence: He returned to the United States near Boulder, Colorado in 1935, and then in late 1946 settled in Los Angeles, California, and became a very important force in American bonsai art in the 1950s-60s.
Split into simpler sentences: He returned to the United States near Boulder, Colorado in 1935, and then in late 1946 settled in Los Angeles, California. He became a very important force in American bonsai art in the 1950s-60s.