

According to the 2009 International Survey conducted by Today's Gamers, the percentage of Americans who play videogames is higher than any other nationality. Not only that, but we spend way more time playing videogames than other countries. Of all the respondents to the online survey of dudes over 8-years-old, 87% said they "played computer games*", spending an average of 11.5 hours a week. Second place in terms of population percentage was Britain, where only 74% of dudes said the played computer games. Second place in terms of time spent was France, where the dudes who said they played computer games spent an average of 7.1 hours a week.
Ha, not even close. USA! USA! USA!
There are more charts from the survey here.
* Note this terminology flings the door wide-open for people who play Minesweeper, Wii Fit, and that farming thing on Facebook.