Union members bled and died to get those regulatory protections in the US.

Is that supposed to mean something? lots of people died for the Third Reich, but that doesn't validate it.

It doesn't mean it's good, it means some people cared about it very much.

You don't have to be a member of a union to work in particular trade in the UK, apart from maybe Doctors who have to be members of the British Medical Association which I think is a regulatory body and a union combined although I might be wrong about that. For example Teachers, I think there are a couple of different unions they can choose from but they don't have to be in one of them to be a teacher. Is that different to the US?

In the US, there can only be one union by law.

If you don't like it, you can't pick or make another.

By us law, you are usually allowed to quit the union, if you do, you still have to pay the union part of your salary.

In the US, workers can't join or start a union unless 51% of all workers vote to join them/let them.

If all this sounds crazy, polarizing, and like a recipe for conflict, you are correct. I think the European versions of unions makes much more sense, and are closer to free association