Another social faux-pas

Sitting at dinner party last night talking about Hugh Laurie's skill at doing an American accent in House. I'm blathering on about how Stephen Fry says he met him for lunch on set and Hugh had to keep talking with the accent so he didn't lose it.
A dinner party guest says :"That's so strange as I never think of Americans as having an accent."
There is a pause before I say, "You don't think Americans have an accent? How do you describe how a British person speaks then?"
At which point my husband pipes up, "Don't get her started. Shall we change the subject?" and laughs nervously. (see previous post Only words)