That's a mixture of minor pitch correction (she can sing OK) and intentionally added distortion artifacts to make her voice "stick out." If you want to hear the same effect taken to the extreme, the old "Transformers" cartoons from the 80's all used the same effect but much more obvious imparted by a vocoder (the plugins her producers use are vocoder emulations) to have a human and robotic voice at the same time. Wally Burr Studios did all the audio post work for that. So the next time you have to suffer through one of her synthetic tunes, picture her as a robot that transforms into something else.
Carrie Underwood? Another faux-country singer famous for winning yet another rigged TV talent contest.
