You have a 21st century union model that works, Joerg.
Here, the union advocates want to use an outdated 20th century model that keeps unions and corporations at each other’s throats as adversaries. In that model, it is unsurprising that corporations try to break down the power of unions. The old adversarial model is outmoded and has run its course.
Further, unions in the US have brought on a good deal of their own troubles by totally aligning all their political activities (and the nontrival political contributions gleaned from union dues) totally with one political party. Again, this makes them the natural political enemy of the other party, which otherwise would have no ideological quarrel with worker collectives.
All in all, unionism is pretty much dead in the US. There is one rather significant piece of federal legislation which keeps them on life support, but other than that…….not much.