I don't think she defected as such. After September 11 the WTA gave players the oppotunity to play under different countries if it was possible for them to do so and seeing as Kim is married to a Swiss guy she decided to play under the Swiss Flag in the tournaments that where going on at that stage. She is still listed on the official WTA doubles rankings as representing the US so I think that is was only a temporary thing. She said during the Swisscom Challenge last year that since Sept 11 she felt safer playing in Europe under the Swiss flag rather then the American.