Complex sentence: The Packers initially played teams from Wisconsin and Michigan's Upper Peninsula; however, the success of the team in 1919-20 quickly led to its joining of the American Professional Football Association, with the league changing its name to the National Football League in 1922.
Split into simpler sentences: The Packers initially played teams from Wisconsin and Michigan's Upper Peninsula. However, the success of the team in 1919-20 quickly led to its joining of the American Professional Football Association, with the league changing its name to the National Football League in 1922.