American cultural influence on UK teenagers was clearly substantial by 2011: the BFI’s 2011 Statistical Yearbook says US films accounted for 71.8% of UK box-office gross in 2010, and that USA plus UK studio-backed films had stayed around a 90% combined share over the previous decade. The Official Charts Company’s 2011 year-end singles list also shows many major hits by American acts such as Maroon 5, LMFAO, Rihanna, Pitbull, Bruno Mars, Jennifer Lopez and Lady Gaga. But the claim is too broad if read as saying teenage influences were mainly or overwhelmingly American, because British acts and British-made content were still highly prominent too. So the statement captures a real trend, but it overstates how exclusively American the influences were. Sources: BFI Statistical Yearbook 2011 (https://core-cms.bfi.org.uk/media/924/download); The Official Charts Company, “The Top 40 biggest singles of 2011 on the Official Chart” (https://www.officialcharts.com/chart-news/the-top-40-biggest-singles-of-2011-on-the-official-chart__1723/).