Complex sentence: Many local humane societies were founded earlier, and are independent of these similarly named organizations, therefore, local humane groups called SPCA or Humane Society are not related to the national groups such as the Humane Society of the United States or the ASPCA.
Split into simpler sentences: Many local humane societies were founded earlier, and are independent of these similarly named organizations. Therefore, local humane groups called SPCA or Humane Society are not related to the national groups such as the Humane Society of the United States or the ASPCA.