Part is also that only 10% of American workers belong to unions; as rare as union or guild* strikes are, strikes by non-union employees are, if not completely non-existent, exceptionally rare.
*- Most of the workers’ organizations in the entertainment industry are “guilds,” not unions. My understanding of the distinction is that a guild provides collective bargaining for independent contractors (actors, writers, directors, etc.), while a union does the same for actual employees.