The data here seems to indicate otherwise
https://www.epi.org/publication/latest-data-release-on-union...https://www.npr.org/sections/money/2015/02/23/385843576/50-y...
Now it's true I have not lived all over the world, but I have lived in numerous places in the U.S, in Denmark, and spend some time in Italy every now and then. I also lived in Germany as a kid, but I've never really seen these fearsome unions you are familiar with, and did I say again I am in Denmark? Even here it isn't like such a powerful organization.
Certainly one can find historical instances of powerful unions, but they do not seem to exist now, and thus your analysis must be faulty somehow. If unions are naturally more powerful than the other forces of society their power should always increase and not decrease, but as the data linked above shows the opposite is the case.
If you want people to accept your logic you will probably need to back it up with data, arguing about real world things like unions tend to bring forth such requirements.