The outspoken star - who was a judge on the UK version of the show for four series until 2007 - thinks Nicole Scherzinger, who was a guest panellist on the British programme this year, would be a much better choice.
She said: "Nicole would be amazing, she's great TV, has a huge following over in the States and people absolutely love her. Plus she's beautiful and talented.
"Cheryl's perfect for England - she's the nation's sweetheart and they absolutely love her. But In America it's Nicole's town. You have to think of the audience and most of them have never heard of Girls Aloud."
Despite her comments, Sharon still believes Cheryl has what it takes to be a star in the US, particularly as she is planning to relocate to Los Angeles.
She added to Now magazine: "It takes a long time to make it in the States because it's so huge. I think she's made the right decision to move out here. She couldn't just come over here to do a show then go off. You have to work at it."
Sharon - who left the UK show due to rows with fellow judge Dannii Minogue - accepts it is unlikely show chief Simon Cowell will ask her to return to 'The X Factor'permanently - because she is too old.
She admitted: "I think Simon needs his young girls beside him, like Nicole. If you were king of the world like he is, would you want ugly women around you? He's not going to want someone with no teeth and psoriasis - that's why he has beautiful girls around him."