Complex sentence: After becoming popular in southern California it eventually became popular all across the United States by the 1980s, and is also widely known in Japan, where any roll containing avocado as an ingredient is informally referred to a california roll.
Split into simpler sentences: After becoming popular in southern California it eventually became popular all across the United States by the 1980s. The roll is also widely known in Japan, where any roll containing avocado as an ingredient is informally referred to a California roll.