GrumpyOldMan said:
I can’t say, never having been involved in a DnD game refereed by an American.
To a great extent, I suppose that it’s up to the referee how royalty is portrayed, and which historical model is used.
Actually, I think it has a lot more to do with the literary model used. IME, D&D isn't generally based on history except in a roundabout way. It's much more generally based upon literature. So, how the king is treated will depend upon the game:
-Fear, Respect and Loyalty: A Robin Hood (vis a vis the true king of course), Lord of the Rings, or King Arthur style game.
In this model, the king is just (though his regents may be crooked and rebelled against) and powerful and will generally be followed loyally. This is a rare model in modern literature and cinema--partially because the king is an authority figure and the dominant forces of our day see that as sufficient reason to be disrespectful and subversive, and partially because it's very rare to see justice and goodness presented non-ironically. (Even Peter Jackson couldn't bring himself to do so wholeheartedly in the Lord of the Rings films, as demonstrated in the way he screwed Faramir's character and changed Elrond and Aragorn).
-Loyalty (The Three Musketeers, James Bond, etc)
In this model, the king is a figurehead. He (or she in the case of James Bond) may or may not be ineffectual but is rarely relevant to the plot. Rectifying injustice is up to the PCs and this knowledge inspires a certain free-spirited attitude where "minor" indiscretions (whether they are pretending not to be able to hear the Queen's representative in the closing sex-scene or duelling with the cardinal's guards and romancing the queen's ladies in waiting) are expected to be overlooked by the monarch.
-Rebellion (The Star Wars series, Willow, etc).
In this model, the king is the source of evil and injustice and his is who the PCs are fighting against. In some fiction this may be done in favor of a different claimant. In the classical stories, it would be done in favor of the true king whose throne the current king had usurped (Prince Caspian). IME, however, for most modern stories, the fact that the protagonists are rebelling, however, is far more important than what they are rebelling in favor of. Braveheart talks a lot about freedom and only a little about the rightful king of Scotland. IIRC, the original StarWars trilogy managed to finish without ever mentioning that the rebels were going to set up the New Republic (or whatever it's called).
I'm sure there are more literary models of rulership than this suggests and that the amount of class consciousness and formality in society (in America, most people seem to want to be on a first name basis--Miss Swan's "call me Elizabeth" line at the beginning of Pirates of the Caribbean was perfect modern American egalitarianism) plays a role in how characters interact with monarchs and other important people. However, I suspect the dominant literary model of the campaign's treatment of the monarch is even more important.