... fan of Avalon and Harbeth, it's safe to say that this is my preferred sound ...
What makes you think Avalon (Acoustics) is British?
It is made right here in the USA (Colorado to be specific).
I think, if there is an American sound, that the stereotypical, (no pun intended!), American speaker is a full range speaker. And so the Avalon speakers, are a perfect example of said sound. (Americans tend to have larger houses, which are more spread out, and hence the ability to have bigger, louder and more bass heavy speakers. This is a generalization of course, but since we are using stereotypes, it makes since to generalize.)
My two cents worth anyway.