When you think about it there probably isn't a single country that has tennis as their #1 sport.
It's the same where I live, Footie, footie footie. Tennis is an enigma of a sport. Appreciated all over the world where even sports like Football (/Soccer) is completely ignored in certain parts, but Tennis is never the biggest thing in any country. Many people all over the world acknowledge tennis due to the hype created by the grand slams and the biggest players and that tennis has always been one of the traditionally known sports.. I mean, nearly everyone knows who Federer is.. but those same people might not even know how the sport works.
For example, last year I was watching the WTF 2010 Final with a group of friends in a restaurant. I was the only one watching it by the way. I was sitting too far away and with my crappy eyesight was unable to see the score. I asked a couple friends (who are completely ignoring the screen) to tell me what the score says and they say- "errr, oh Federers playing! Nadal has 3, 6, 1 aaand 0 .. Federer has 6, 3, 2 and 15." Sounds incomprehensible until you realise they were reading the score sideways.. should have been 3-6, 6-3, 1-2 (0-15). Pretty sure I would have foamed at the mouth if it wasn't already stuffed with a kebab.