Emma's right there - people poke fun at the Royal Family all the time. Even if someone objects to that it's generally because they feel sympathy towards the targets as human beings, not because of some sense of offended patriotism. There are always exceptions of course, but they'd be likely to be seen, correctly, as oddballs, and you get those anywhere.)

...............

In my opinion in a democracy the people are responsible for the political system. That would imply there was some practicable way of changing that system - and that certainly doesn't really seem to be the case with the US system, even more so than in other places.

For example, if the Scots decide they want independence, and vote for it, they'll get independence. (The English have learnt a bit from their Irish experience.) If a majority of people decide they want rid of the monarchy, and vote in a Parliament where the majority is committed to abolishing it, the monarchy will be eliminated.