I think everybody is pleasantly surprised to hear native English speakers master a foreign language, including their own. It is well known that native English speakers don't usually have the same motivation to learn a foreign language. As a result only those who are genuinely interested and motivated even get as far as a half decent level of fluency... It is different for people who more or less have to learn English as a foreign language. It would probably be quite a novelty in Russia, to hear an American speak good Russian! Or an English person. I know an American who lives in London now, but lived in Moscow for 3 years before moving there. He only learnt a few words of Russian during this period, and said it was "impossible". He worked in banking and I suppose he was able to get by in English at work. I have noticed that American and British accents sound quite different in Swedish and in French. The British accent is less characteristic and could be mistaken for something else unless the person isn't very obviously British. The American accent is much more obvious since American English has some rather unique sounds that makes it stand out. But there are exceptions - I once heard an American speak beautiful French with only a very faint accent - obviously he'd made a big effort. Americans are usually outgoing and and friendly, so accent or no accent - that helps to make a positive impression!