She tried her solo career in the US in 2007, 2009 and most recently in 2011 with the X Factor US, but the other girls from PCD sabotaged her image with stories etc, which may or may not have been true.
Either way it damaged her reputation in the US, and she was largely seen as the person to blame for the split of the band which was a shame.
Which was stupid, as the "band" was only ever her and a bunch of glorified backup dancers/singers. It's not her fault that the rest were back ground noise.
Nicole is great, I dont care if she never goes back to the US, she can stay over here and be on tv for ever as far as Im concerned.