Canadian teen idol Justin Bieber swept the American Music Awards on Sunday, overshadowing Eminem to take home four prizes, including artist of the year. The fresh-faced pop singer also won statuettes for favorite pop album, breakthrough artist and favorite male pop artist. Since the awards are determined by fans' online voting, the 16-year-old star was unquestionably the frontrunner. His millions of young female fans reportedly account for a hefty portion of overall Twitter messaging traffic. Eminem and country trio Lady Antebellum, who led the contenders with five nominations each, had to make do with some scraps. Eminem won a pair of prizes in the rap/hip hop field, losing to Bieber in his three other categories. He did not attend the event at the Nokia Theater. Lady Antebellum was named best country group. R&B singer Usher, who helped discover Bieber about 18 months ago and signed the youngster to a record deal, also won a pair of prizes. The two embraced on stage after Bieber collected his artist of the year trophy. "I don't cry that often but I did, and I enjoyed it," Usher told reporters backstage. During his trips to the stage, Bieber repeatedly thanked his fans and reflected on his unlikely rise to fame. "I'm from the smallest town in the world of, like, 30,000 people," he said as he accepted the breakthrough artist award. "I never thought this was possible." CANADIAN INVASION Bieber, who was raised in Stratford, Ontario, but now lives in the United States, is perhaps the hottest new commodity in the music world. His album "My World 2.0" has sold almost 2 million copies in the United States since its release earlier this year, and his public appearances turn into mob scenes. It ended up being a great night for Canadians. Michael Buble, 35, won his first-ever award, for favorite adult contemporary artist. "While you Americans are sitting getting fat, us Canadians are getting ready to take over," he joked backstage. British rock band Muse was also a first-time winner, for favorite alternative rock artist. Other winners at the 38th annual ceremony included country stars Taylor Swift, Carrie Underwood and Brad Paisley; funk band the Black Eyed Peas; R&B singer Rihanna, and Colombian pop siren Shakira.