From which year did Martina Navratilova compete officially as an American rather than a Czech player?

Originally from Czechoslovakia, she was stripped of her citizenshipwhen, in 1975 at the age of 18, she asked the United States for political asylum and was granted temporary residency. At the time, Navratilova was being told by the Czechoslovakian Sports Federation that she was becoming too Americanized and that she should go back to school and make tennis secondary.[ Navratilova became a US citizen in 1981, but on January 9, 2008, she had her Czech citizenship restored.[5She stated she has not renounced her American citizenship nor does she plan to do so and that the restoration of her Czech citizenship was not politically motivated.