“American Idol” sells the illusion of stardom. The exalted talent show offers hopefuls a chance to cut out the difficult bits – the endless gigs in bars, the countless long nights spent in a packed van heading off to a show that may or may not have a payday at its conclusion, the hours and hours spent wondering if you’re ever actually going to get anywhere – and proceed straight for the victory lap. Those who win, or place high ... well, they end up with an instant high-profile career. They might not be ready for it, having done little of the actual work that prepares one for such things. But by the time they realize this, it’s already too late. The contracts have been signed.

Carrie Underwood, who took top honors in the 2005 edition of “Idol,” is in possession of a miraculously powerful voice. She made this point abundantly clear throughout an exuberant, close to sold-out show at First Niagara Center on Tuesday. It was also clear, however, that massive stardom may have come her way before she was fully prepared for it.

As flawlessly as Underwood sang her bits Tuesday, she never appeared to be altogether comfortable on stage. The music itself was certainly constructed in the interest of conveying deep emotion – at times, of the overtly melodramatic variety. Yet through it all, Underwood never seemed to be able to fully connect with her audience.

This might sound surprising, given that Underwood and her band have been performing around the world for several years. The “Blown Away” tour itself commenced life in 2012 and has already seen Underwood play for some 500,000 people. Tuesday’s show felt like musical theater, however – it all came across as scripted, and the lack of spontaneity, combined with Underwood’s rather aloof presence, suggested a barrier between performer and listener.

Underwood and her eight-piece band earn high marks for their professionalism, it must be said. From the opening moments of “Good Girl” forward, things went off without a hitch, the band members providing an immaculate, if largely soul-less, recitation of the evening’s program, and Underwood herself hitting all of her notes with a full, pitch-perfect delivery.

Though niche-marketed as a country artist, with country hits and platinum sales to back up such an assertion, most of Underwood’s show favored mainstream rock and Top 40 pop over country. “Good Girl” and its follow-up, “Undo It,” have about as much to do with country music as does Def Leppard’s catalog. But with her third number, the mid-tempo “Wasted,” Underwood proved that she can sing country music with warmth and virtuosity. Early on, a cover of Randy Travis’ “I Told You So” provided the singer with a chance to truly shine.

Less convincing are the rockers – the saucy “Cowboy Casanova,” and the Bon Jovi-esque “Two Black Cadillacs” both came across as at best play-acted, and at worst, forced and disingenuous. Then there was the gospel-tinged country-pop “Jesus Take the Wheel,” a rather confusing bit of sermonizing involving a narrator who seems to have taken the “God is my co-pilot” thing a bit too literally. But Underwood gave it her all – which is a considerable amount, be assured – and much of the house sang along.

Aside from Underwood’s outfits, which were startlingly tacky prom-dress hybrids that would flatter no one, the stage set and the production itself were relatively tasteful. A combination of films, still photography and subtle lighting cues served to create a rock show atmosphere, even if some of the films displayed Underwood attempting to outrun a twister in the middle of a prairie or cavorting about in slow-mo.

At the show’s high point, Underwood and most of her band boarded a satellite stage made to resemble a front porch, presumably in the South. The platform lifted from the ground and was carried by wires out over the crowd and toward the back of the arena, offering Underwood an opportunity to get up close and personal with the broad expanse of the venue. The folk-pop of “All-American Girl,” the mid-tempo rock of “Nobody Told You,” and the faux-reggae of “One Way Ticket” – which came replete with bursts of confetti and the unleashing of several massive beach balls, to the crowd’s delight – had the whole place on its feet, and provided the emotional apex of the show.

Yet, despite the bells and whistles, Underwood never appeared to be entirely comfortable. Her voice can certainly fill an arena ably, and when she tackles legitimate country music, she shines, unquestionably. The whole spectacle of arena-country just didn’t seem to suit her, however. She’s the sort of singer who sounds best when she just stands there and sings. Unfortunately, American Idol winners aren’t afforded such luxuries. They have to be larger than life pop icons, even if that isn’t what they were cut out for. I, for one, would rather hear Underwood sing legitimate country music in more intimate surroundings.