Your heritage was not the correct one for you to hear what high caste Englishmen, or even most high caste Europeans think of Americans. Rest assured it is as prejudiced and unflattering. Even the Irish are often not good enough.
My heritage notwithstanding, most Brits assumed I was an American and treated me as such, which, as you say, was unflattering.
The fellow who made the quote about Islam was more a humble academic than an arrogant upper-class Brit (or, even worse, an upper-class wannabee--commonly found in areas such as Chelsea in London). I don't mention his name because I presume the comment was made in confidence.