i realize i am of course doing major mental gymnastics here (probably because i just don't understand politics on your level), but do you think it's possible that these constitutional monarchies all function along similar lines because they share a common cultural and developmental heritage? like maybe the fact that they are all european is not a complete coincidence? i could be wrong, but it just seems like they're all pretty closely related to one another in space and time, so maybe we should be cautious about overgeneralizing from what is clearly not any kind of random sample.
I'm not sure what point you think you're making. Like, yes, political culture is a very important part of any political system that relies heavily on convention? Did that need to be pointed out?
perhaps i am misunderstanding your point in general — and of course please point it out if i am — but imo you seem to be making the claim that constitutional monarchies are very democratic because they always have impotent executives, and impotent executives are good. others have pointed out that this is not a necessary feature of a constitutional monarchy. we can easily imagine a constitutional monarchy with a strong executive.
your argument, then, was that all current constitutional monarchies have this feature, and we can/should generalize from this fact — after all, what are the odds that they would all share this feature by accident?
this brings us to my argument above: the fact that those governments all share a similar heritage/culture/time in history/etc means that we ought not generalize from their shared features. they aren't random and independent measurements. there are clear covariances.