Question: Who is/was the most influential singer/group in the United States in the past 15 years? 

Answer: The last 15 years? Well, that would either be Michael Jackson or Madonna. Both created their own unique sound and had many other artists in the past several years come out and try to be like them. For Michael, that would be Usher, Justin Timberlake, and the like. For Madonna that would be Britney Spears, Christina Aguiliera and the like. They were both massive pop icons in the 80's and 90's. While Michael has lost most of his American following due to his legal issues, he is still one of the top recording artists in European and Asian countries. Madonna, on the other hand, continues to re-invent herself with each new album. This is shown in her most recent release of "Confessions on a Dance Floor". She's physically in the best shape she's been in for several years and her sound still makes people get up and move.
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