The London 2012 Olympics 'was the most watched TV event in US History'

"Roughly 217 million people in the United States watched the London Games, making it the most watched television event in history. And unlike other big, live events like the Super Bowl or the Academy Awards, the Olympics offer researchers a prolonged, 17-day period during which to study behavior.
That sandbox showed that eight million people downloaded NBC’s mobile apps for streaming video, and there were two billion page views across all of NBC’s Web sites and apps. Forty-six percent of 18- to 54-year-olds surveyed said they “followed the Olympics during my breaks at work,” and 73 percent said they “stayed up later than normal” to watch, according to a survey of about 800 viewers by the market research firm uSamp.
Forty-six percent said they “delayed doing laundry and other household chores” to catch events like gymnastics, where the United States inched out a win over Russia and Romania for the gold, and swimming, where Michael Phelps narrowly came in second in the men’s 200-yard butterfly."

Source:  New York Times, 25th September 2012

Note - As I pointed out when the UK figures were reported, it's not that helpful to compare a sporting event spread out over more than 2 weeks to a single televised TV event