Samsung, Apple's arch-rival, shipped 16.8 million handsets for a 32% market share in the country, reported Xinhua.
The report said Apple's success has been driven by its popular ecosystem of iPhones and App Store, generous carrier subsidies and extensive marketing around the new iPhone 5 model.
However, Apple's hard-won victory is expected to be short-lived. Samsung had been the No.1 mobile phone vendor in the US since 2008 and it will surely be keen to recapture the title this year by launching improved new models such as the rumored Galaxy S4, Strategy Analytics said.
Meanwhile, the report pointed out that despite a solid fourth-quarter performance, the US mobile phone market had contracted for the first three quarters of 2012, making annual mobile phone shipments fall by 11% in 2012 from the year of 2011.