> Stuff like 'everyone who works has to be union'
So-called closed shops haven't been legal in the U.S. for 75 years, and union shops for over 35 years. What you're probably thinking of are compulsory agency fees, which admittedly have escalated to as much as 1/3 to 2/3 of full union dues. Full union dues are typically 1%-3% of wages. (According to the Teamsters website, full monthly dues are 2.5 times hourly wages, which IIUC is 1.5%, assuming 40 hours per week and 50 weeks per year.)
But the Netherlands have mandatory Works Councils for any company with 50 or more employees, and the company is required to pay all the expenses, including legal and litigation expenses of the councils. So it's functionally the same thing, except the cost is hidden from the employee.
Granted, the relationship between management and workers is much less hostile in Europe, so transactional costs are presumably substantially less. I wouldn't be surprised (but can't find numbers) if Works Councils budgets or comparable budgets for equivalent union representation are much less in Europe. But I also imagine the wage premium that union power in general provides European workers, whether workers are in a union or not, is substantially greater than in the U.S., so overall "costs" (i.e. surplus value shifting) incurred by corporations would be greater.
Because management has always been so hostile to unions in the U.S., unions certainly have had to fight harder, and there's consequently more friction and acrimony. But it doesn't seem particularly fair to place that blame only on unions. IMO, management is much more culpable in that regard, but from a third-party observers' perspective one could easily simply chalk it up to American culture (and especially business and work culture) in general.