Unions in the EU have very different rules than unions in the US. In particular, American unions can essentially force an employer to become a "closed shop" through a majority vote. Everyone who works there then has to pay union dues and accept a union contract. EU unions involve more worker choice.

That's simply not true in Alabama and many other states, which legally prohibit closed shops.

In Poland it's not normal outside of some industries, and the unions there can be a mixed bag (old people from Solidarność being detached from reality for example).

People in America have been subjected to nearly 100 years of very successful anti union propaganda. They used to be very strong, but have since been eroded and vilified by capital.