The differences were made law with the Taft-Hartley Act of 1947. I.e. sympathy strikes are illegal in the US, so the only real power left to unions is jealousl

The differences were made law with the Taft-Hartley Act of 1947. I.e. sympathy strikes are illegal in the US, so the only real power left to unions is jealously guarding the petty pearls available to them.