Happy to give my take on the answer to that. What would happen is that the rich would get very slightly richer, in most cases negligibly so. The less privileged classes would suffer existential crises affecting their health, their families, and their entire lives. In the US plutocracy in particular, where the gap between rich and poor is one of the biggest in the civilized world and growing ever larger, the widening gap would create suffering and social instability, driving up crime of all kinds, both violent and non-violent. Racists would come out of the woodwork and blame the social unrest on immigration and brown people.
So, much as I’ve been pointing out many of the issues with unions, on balance they’re a good thing and generally essential. But like government itself, which is essential and generally beneficial, unions are problematic when they get out of control and become unchecked self-serving powers.
Gap between rich and poor, and recent trends (the higher the Gini coefficient, the greater the inequality gap):