Thus the powers unions obtain not only in the US but also for instance the UK, is entirely predictable - nothing stops them taking over the firm and unions are very frequently run by open communists who see it as a moral imperative to do so.
A good example is Unite in the UK, run by Len McCluskey:
https://en.wikipedia.org/wiki/Len_McCluskey
In a speech at the 2010 Durham Miners' Gala he said political developments in Cuba and Venezuela should be better known, and suggested the reason they were not was because of "the fear of the good example".
Not surprisingly when major unions are led by people who think Venezuela is a "good example", people learn that unions are bad news!