For the US, there may be historical cultural reasons as well. Some unions were actually run by mafias. These are the same kinds of groups that would go around neighborhoods asking for “protection” money. If you don’t pay, you don’t get protection from their henchmen ruining your store.
Of course, the US also has a history of anti-union forces effectively being armed paramilities who would break up even the lightest of strikes or labor movements with public violence.
