I wonder how Koreans would be represented in this study? When talking about teens, I dare say that they might be closer to the Chinese than the Americans.
I’m also going to guess that these numbers have changed substantially in the US. The use of social networks has exploded in just the last couple years.
However, the question here might be culturally biased, “I live some of my life online.” I would guess that most Americans would say that I spend time online, but it’s not my life. This is a subtle difference, but one that could certainly skew the results. If the questions asked simply how much time was spent online, the answers would be very different.