When Susan Boyle became an Internet sensation earlier this month, part of the appeal to audiences had to do with her voice, but an equal measure may have hinged Simon Cowell's stunned expression. For one brief moment, the "American Idol" and "Britain's Got Talent" judge's face went from reliably smug to unguarded and amazed. It was like watching the Grinch's heart grow three sizes.

So when Cowell met with reporters last week to promote the premiere of "America's Got Talent" at an NBC summer press day, it's little surprise that he faced a number of questions about Boyle and her appeal.

"Listen, what's great about Susan is that it's the story of the underdog, isn't it? ... I wouldn't have sat here five weeks ago and said the person to watch out for is Susan Boyle," Cowell admitted. "She was just one of a group of very good auditions. But when the story plays out, it either works or it doesn't. And it's why we came up with this show in the first place, which was to come up with one show where there were no rules, to say that whatever you do, you can audition. You can do whatever you want. You can be whatever age you are. And, you know, we were all guilty on the panel of judging her before she sang and got it completely and utterly wrong. And you watch it back, and it's embarrassing. But, you know, it was a good thing. It's one of the reasons why she's so successful."

While "America's Got Talent" has been a reliable summer performer for NBC, the show doesn't have the same breakout hit reputation as "Idol." Cowell said that Boyle may help change the show's stature on this side of The Pond.

He said, "I think with regards to this show, I am seriously thinking now that we should hold maybe two more -- NBC don't even know this yet -- two more open auditions off the back of Susan Boyle since the awareness is that much higher, to say 'By the way... you don't have to be a singer who's 47 who's never been kissed, with a cat, just somebody who says, 'You know what? I think I could win a competition, and I think I am talented, and I don't think people are going to judge me because of the way I look.' So I think it's a positive thing for all of us."

Cowell did point out, though, that all of this international adulation for Boyle is on the basis of a single televised audition, plus one or two old audio clips. As anybody who's watched "America's Got Talent" can tell you, the show's audition rounds are epic and Boyle still has a long way to go to win the competition.

"I've got an option to sign her, but I keep saying to everybody that first of all, she's got to win the next stage," Cowell said. I mean, the problem is with all the sort of the substories about the cat, way she looks, I'm not interested in this anymore. And all the kind of the gimmicks. It's her. She has got four weeks to prepare for the biggest night of her life, which is she's got to sing better than she sang before with all that expectation on her.  And then if she gets through to the semifinals, she may get through to the final, and then she may win the show. But it could all go horribly wrong now because there's so many other distractions. And this is -- you know, for her, it's about her singing career."

Cowell's fellow "Talent" judge, Piers Morgan, said that, regardless of how far she advances on "Britain's Got Talent," Boyle has thrown down the gauntlet.

"Obviously I've done interviews all day, and there's only one subject in town: Susan Boyle. I think that's going to be very good for 'America's Got Talent' because I think that Susan Boyle has laid down the challenge," Morgan said. "Forget the Ryder Cup. This is the big one. Has America got its answer to Susan Boyle?  I don't mean a 47-year-old woman from a little town. I mean a talent that comes out of nowhere that can really stun and amaze Americans.  And I think that the answer so far from what I've seen is yes."

"America's Got Talent" premieres on Tuesday, June 23 with a two-hour episode airing from 9 p.m. to 11 p.m. ET.