for Navratilova and Lendl, either Czechoslovakia and / or USA, but Czech Republic doesn't make any sense, as the country did not exist yet when they became American citizens.
Same for Monica Seles. I would accept Yugoslavia and USA, but she never played (or lived) with Serbian nationality.
Martina Hingis has always played as a Swiss citizen
Yes, that is why I quite clearly state MODERN countries. You see, It's like when Italy is accepted as the nationality/birth place of Leonardo da Vinci even though it was hundreds of years before Italy even came to existence.
Same for Monica Seles. I would accept Yugoslavia and USA, but she never played (or lived) with Serbian nationality.
Martina Hingis has always played as a Swiss citizen