Many an American Idol winner has had difficulty transferring their success on the show to success on the Billboard charts, at least for any longer than a few months. Don’t tell that to country megastar Carrie Underwood, though; from multiple Grammys to multiple platinum records, Underwood has virtually dominated Nashville, and America, since 2005. Yet the Carrie Underwood of that Idol finale and the Carrie Underwood of late 2009 is, for better or worse, practically the same performer, a cheery, charming performer whose girl-next-door persona belies her talented pipes and ridiculously good looks. Still hitting the same notes, still achieving that equilibrium between country roots and mainstream pop, Play On is an apt title for Underwood’s third effort, an album that does little to stretch beyond what came before. It’s not that what Underwood has done before is all that bad; on the contrary, some of her previous singles have been some of the best the genre has had to offer, and debut Some Hearts was an earnest, energetic record that, while shallow, was a pioneer of the new wave of country-pop records. Nowadays, though, her shtick is old news, and it’s been co-opted by artists like Taylor Swift, talents younger and more in-tune with contemporary audiences than the relatively old Underwood. When Underwood sings about heartbreak and cheating boyfriends on songs like “Cowboy Casanova,” it lacks the emotional honesty of her younger peers or, worse, comes off as contrived, lovesick longings…