We can laugh quietly or really loudly. We can titter behind our hand. If we have a surprising thought, laughing may occur involuntarily. Giggling, especially prolonged giggling, as when a child is tickled and is delighted to be tickled, can go on for quite a while.
The queen famously said,"We are not amused" but I haven't heard that she said, in an equally restrained way, "We are amused."
It seems likely to me that the queen saw and heard many things, both privately and publicly, that seemed amusing but at which she declined to laugh or even smile.
American pragmatism is often attracted to whatever works successfully. It may be that the best or most appropriate or accepted manner of laughing in one situation is not optimal in another. Sometimes, we are in a situation where laughs are prompted so steadily that we just keep a smile locked on our face. I don't know if a person can get hoarse from too much laughter but I suspect it is possible.
