Do you speak American?

People here in Italy often ask me if I speak American, as if there were grand differences in the British and American versions of English. Apart from the annoying variations in spelling and slight differences in grammar usage, we use the same language. Of course George W. Bush thinks that Mexicans speak Mexican, and he did receive a resounding applause for this statement. I may have posted this before, but Italians, depending on the region, often don't speak Italian. A great majority of people here in Northern Italy prefer to speak the local dialect, which here in Trentino subdivide further into each little valley. Often communities that are no more that 50 miles apart have difficulty understanding each other's dialect. Maybe this is the reason that I get asked this question. I have to admit that the question often irritates me. It feels like a criticism -- as if we poor, backward Americans haven't yet mastered the language of our superiors. Although there are plenty of British people that express this same sentiment. Perhaps they teach English here in Italy. There is nothing more annoying than being told by someone, who doesn't speak your language perfectly, that you don't speak your own language correctly.
This can be especially irritating when they use English phrases in their own language in a completely incorrect manner. I know I've written before about pseudo-anglicisms but I've recently discovered a few more. I have found out that Italians use the noun "slip" for "underpants" ("pants" for you British folks). An Italian friend here was surprised to discover that a "slip" was that dress you wear under your dress. Interestingly, the term "noprofit" is used instead of "nonprofit." This one is a bit baffling as "non" is the term for negation in Italian. I have searched on the internet to discover if this usage exists in Britain, but found only a website in Italian. I realize that the English language has absorbed and altered foreign words also, so don't break my chops on that issue. This is my soapbox.
Well enough of my lamenting. Thankfully all minor irritations usually pass. Or as my husband says, "time heals all non-fatal (or should that be no-fatal) wounds."