So, if we are dealing in generalizations, the thing about the American relationship to British cultural stuff in general is that those Americans who are, ah, well .... educated, they are the ones who like it, understand it, and seek it out. Pick a type of stuff Brits have done, this is the pattern.
This has always been true, because Britain was where Americans got their books from the time of the first settlers up through the mid-20th century. The US that folks now see, the one that is culturally self-reliant, is very recent. For most of American history we looked to Britain for education and culture.
So, this educated caste of Americans likes British stuff, including British humor. The other 67% don’t like it much and don’t look for it, because it doesn’t fit American cultural patterns. Actually, it violates them. Culturally, Americans see sarcasm as rudeness and as harm, as the worst thing you can do within a group of people you are part of (or want to be part of). Sarcasm breaks the sense of belonging in the group. That’s a huge red flag for Americans.
People are referring to Stephen Fry’s remarks at the 2009 Hay Festival, and one thing he talked about there specifically was how Brits are raised “from our nanny’s knees” to expect debate and contention, to argue fiercely. There was no American there to reply: yes, and Americans are raised with the saying “if you don’t have anything nice to say, don’t say anything at all”.
Not liking something doesn’t mean you don’t understand it.
I’m the rare American who will defend American humor with its facetiousness and character types. I say that actually no, often British people do not seem to fully understand it — or to find it funny. But then, American humor violates British cultural ideals — it’s based on playing with earnestness, on broad character types and not specific flawed characters. It also has a different pattern of delivery than British humor.
Not liking something doesn’t mean you don’t understand it.