> In the US, that kind of coordinated cross-discipline striking is explicitly illegal (I'd have to go look up my history to confirm, but I believe that was related to the federal intervention to stop the rail strikes because it disrupted mail delivery).

No, it’s just a straight up federal law that bans striking in the railroad and airline industries:

https://railroads.dot.gov/sites/fra.dot.gov/files/fra_net/16...

https://en.wikipedia.org/wiki/Railway_Labor_Act

The US’s people (by proxy of its democratically elected leaders) believe some workers deserve fewer rights than others.

It isn’t so different than an informal caste system, except it is far more flexible and allows a few to break through, especially if they can prove their economic mettle. The US makes a lot more sense once you realize much (the majority, I would say) accept that some people deserve more than others.

What is most important is trying to not be at the bottom, and staying ahead of those below you. Another easy example is the superior unions for cops and firefighters, who are typically used to maintain the status quo (similar to a king’s guards). These union members will readily support leaders who want to weaken other unions.