Complex sentence: The country's governing body for the sport, the United States Soccer Federation (also known as the USSF or U.S. Soccer), oversees the system and is responsible for sanctioning professional leagues, and the leagues themselves are responsible for admitting and administering individual teams.
Split into simpler sentences: The country's governing body for the sport, the United States Soccer Federation (also known as the USSF or U.S. Soccer), oversees the league system and is responsible for sanctioning professional leagues. The leagues themselves are responsible for admitting and administering individual teams.