I am reading a book about the differences in language in the US and the UK by Erin Moore called "That's Not English". She is an American who has lived in London for some years. She says that British people are likely to be more familiar with American usages of English than vice versa because of the relative dominance of America in the mass media. However, sometimes I still come across from time to time American idioms and usages I don't know. There's a funny interview of Hugh Laurie by Ellen de Generes in which they quiz each other on the meanings of national idioms / words. Funny ones were selected and neither got any of the answers right. Like Hugh Laurie, I knew all the British ones but none of the American ones.

Funnily enough I had a similar discussion with a Japanese friend just yesterday. She spent a year in Canada and was musing about the fact that the Canadians knew a lot about the differences between their use of English and the American way - but the Americans she knew were oblivious to the fact that everyone didn't do things the same way they did. However, I don't think you can ever generalise about a whole country - not all Americans are insular; just as not all Australians are brash and vulgar.

To a certain extent, it is true. I remember once I was standing in line and I asked the person next to me if she was in a queue and she didn't get it.

I think you are right. British/Irish/Australian/NZ/SA people are far more likely to be familiar with American words and phrases than vice versa. It's important to understand that US English is not a 'foreign' language for us. Most of us are exposed to American English from a very early age, starting with Disney cartoons and moving on to Hollywood movies, US TV sitcoms, American music and so on. As English speakers we all grow up with a passive knowledge of American English to such an extent that hearing American words and phrases seems completely normal to us. Young people in Britain and other English-speaking countries particular are essentially bilingual when it comes to listening skills. For example, a small child in Britain understands when they hear that the American family in their favourite US show takes the 'elevator' up to their 'apartment', but they will talk about taking the 'lift' up to their 'flat' in a British context. By contrast, Americans have far less exposure to non-US English. Believe it or not, some British TV programmes for children are actually 'translated' into American English and redubbed for US audiences!

I agree we (Americans) typically are not exposed to English dialects (if I can use that term loosely) from the other English speaking countries. It seems much more common for the rest of the world to be familiar with American idioms due the spread of American movies, TV shows, etc. (as Michael says.) From time to time a phrase from Australia or the UK gets popular depending on what cultural influences are popular.