The tennis enthusiast community is not disconnected with the trouble tennis is facing
in the USA. Tennis is doing just fine. This is a global sport and using Nielsen ratings is an extremely poor way to gauge how it is doing overall.
http://www.bbc.co.uk/news/entertainment-arts-23225146
With a peak audience of 17.3 million, Murray's Wimbledon victory was the most watched Wimbledon final in over 20 years. His SF against Janowicz had 13.2 million viewers.
http://www.abc.net.au/news/2012-01-30/aus-open-final-wins-ratings-battle/3800050
Again, strong Aussie viewership for the 2012 Australian Open final. Eurosport also had an enormous peak audience.
And these are just 2 countries. I don't have statistics for every country, but its not hard to see that tennis is becoming a lot more popular in Asia.
If Tennis was facing trouble in the real world, you wouldn't have Barclays, Emirates, and Mercedes Benz sponsoring the hell out of it. I will start worrying about Tennis as a sport when top tennis players can't find sponsors or are getting 20,000 bucks for winning a grand slam.