Complex sentence: In 2006, it became the first song ever to sell 2 million digital copies in the U.S. and, after another million were sold, it was certified three-times platinum by the Recording Industry Association of America (RIAA) in 2009.
Split into simpler sentences: In 2006, it became the first song ever to sell 2 million digital copies in the United States. After another million were sold, it was certified three-times platinum by the Recording Industry Association of America (RIAA) in 2009.