Complex sentence: From the late 19th century the Second Industrial Revolution in the United States and Germany presented an increasing economic challenge, and the costs of fighting World War I and World War II further weakened the UK's relative position.
Split into simpler sentences: From the late 19th century the Second Industrial Revolution was also taking place rapidly in the United States and Germany, this presented an increasing economic challenge for the UK. The costs of fighting World War I and World War II further weakened the UK's relative position.