The Britain's Got Talent runner-up, 48, belted out I Dreamed A Dream and her new single Wild Horses, a Rolling Stones cover, during the final of the hit US series.
'People were crying and cheering her after her performance,' an audience member tells the Daily Mail.
A beaming Susan, who wore an elegant black dress, then spoke to judges Piers Morgan and Sharon Osbourne.
Earlier in the week, she was snapped going on the children's rides at Disneyland in California.
Her debut album I Dreamed A Dream is due to be released on 23 November.
Watch Susan perform on America's Got Talent here
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