According to gossip website TMZ, the British singer - whose role was confirmed earlier this month - is said to have been replaced on the judging panel by Nicole Scherzinger, who was originally meant to host the show alongside Steve Jones.
It Still Remains unclear why Cheryl has gone and the show's boss Simon has yet to comment.
When her role was announced, Cheryl - who has been a judge on the UK version since 2008, mentoring the winning act in her first two series - said she couldn't wait to get to work.
The 27-year-old beauty said: "I'm so excited to be taking part in the American version of 'The X Factor'.
"I absolutely love it here in the UK, and with the talent they have out In America, I'm sure we're going to find someone very special. I can't wait to get started.
"I just can't decide whether I am more excited to find and nurture the talent or for the unbelievable amount of amusement and entertainment I will have watching Simon doing everything and anything he can to beat me.
"He's tried to beat me for three years in the UK, and hasn't even come close. His ego must be so bruised. America is gonna love this."
Simon - who, along with Cheryl, has quit the UK show - said: "I'm thrilled for Cheryl. She is massively excited about this show, and has been fantastic to work with. She is also a complete brat! Most importantly, this girl can spot talent."