Complex sentence: It is widespread across Europe, North Africa, Asia, and Great Britain and has also been accidentally introduced to North America, Australia and New Zealand where it has become a pest on cultivated cabbages and other mustard family crops.
Split into simpler sentences: It is widespread and populations are found across Europe, North Africa, Asia, and Great Britain. It has also been accidentally introduced to North America, Australia and New Zealand where it is considered a pest on cultivated cabbages and other mustard family crops.