...not only: "AC is mainly used in the United States", but for some bizarre reason it is supplied at a voltage that no other country in the world (is there one?) uses. So not only do you need AC/DC converters but you need AC/AC ones when visiting the states... aaaagh!

Of course, we in the "rest of the world" get the last laugh, as our devices just seem to work with a limp or not at all, however many an American will have fried something or other when visiting us. Recently I heard that a friend of a friend had flames coming out of her hair-dryer when she accidentally plugged it DIRECTLY into the European mains... lol