Boyle said she was humbled by the reaction of the audience and judges.
The Scottish star made it to the final but came in second second place to Ashley Banjo's dance crew Diversity.
Before Boyle's performance, viewers were shown original content from her first audition and life before BGT.
After the performance, Cowell, 59, said: "I can not think of any other contestant who has defined this show better than you".
OK, auditioning might be a stretch, but the Scottish singer did return to the United States version of the talentshow to take part in a Champions edition of 'America's Got Talent', and immediately reminded everyone why she became such a huge star in the first place.
While the Buzzer will advance Boyle straight to the finals, she'll still face some stiff competition from the show's other acts, including several former AGT winners like magician Shin Lim and ventriloquist Darci Lynne Farmer.
Her first audition, a rendition of I Dreamed a Dream from Les Miserables, famously stunned the audience and judges alike.
Still, Boyle says she has "something to prove" on The Champions, and calls herself a champion "for those who don't have the confidence to do things, for those who don't have a voice (and) the ones who people tend to ignore".
Boyle's 2009 debut studio album called "I Dreamed a Dream" became the biggest selling album in the world for 2009.
And with that, Susan Boyle is back. "You're the one. You made a huge difference to a lot of people and I'm absolutely thrilled that you are here".
"I want to be the woman to give you something that you deserve", she said as she stood up and hit the "Golden Buzzer".
Despite being a runner-up on the show, she went on to sell over 25 million records worldwide.
The Tigers and Crimson Tide have now split the last four national titles. "It's been an awesome journey, " Lawrence said. He tallied 295 yards through the air and two touchdowns but threw a pair of key interceptions.
But they have not come anywhere close to qualifying since and have been nearly as bad in attempting to make the Asian Cup finals. Thailand, appearing for the since co-hosting the tournament in 2007, have now won just one of 21 games at the Asian Cup.
The Trump administration has put pressure on the World Bank to justify its lending practices, including loans to China. Mr Kim - who was born in Seoul, South Korea - trained as medical doctor before rising through the ranks at the Bank .
Clemson hit Alabama with a 31-point first half, capitalizing on the Crimson Tide's mistakes and unleashing Lawrence's rocket arm. That led to Travis Etienne's third touchdown of the half, a 5-yard shovel pass from Lawrence.
The leaks began with data from German TV personalities Jan Böhmermann and Til Schweiger, Youtube star LeFloid and rapper Sidos. But no sensitive material on Chancellor Merkel was actually released, a government spokeswoman told Reuters .
He said that they had the " Avengers: Endgame " title was final even before the movie went into production. The theory suggests that it could be possible that Nick and Cap Marvel aren't on the happiest of terms.
Additionally, HTC has partnered with Mozilla to make Firefox Reality the default web browser on all Vive VR headsets. HTC explains that the eye tracking takes place via LED sensors located around the lenses inside the HMD.
President Donald Trump asked aides over the weekend about delivering a primetime address on Tuesday, a White House official said. Congressional Democrats are refusing to pay for a wall. "That's how broken I think some of these discussions are", Mulvaney said.
It was reported earlier that the Jets had interest in interviewing Kingsbury as a possible replacement for Todd Bowles. He was a quarterback at Texas Tech and spent time as a QB with the Jets, New England Patriots and New Orleans Saints.
Both parties signed a pledge at the time to denuclearise the Korean peninsular, though was never clear what this would entail. The news follows speculation earlier on Monday that Mr Kim was possibly on his way to China by train.
Apple's CES ad takes aim at rivals with privacy boast
And while Sony never makes any major game-related announcements at CES , PlayStation will likely have some presence. Apple spent a lot of time in 2018 taking Facebook and Google to task for their awful privacy policies.
20 kids injured after hammer attack at Beijing primary school
The attack comes a day after a Chinese man was put to death for injuring 12 children in a knife attack at a nursery in China. Five children were killed in November when a vehicle ploughed into a crowd outside a school in Huludao in Liaoning province.
Julia Goerges makes tennis history at ASB Classic
The World No. 14 moved on to win a couple of more break points later in the game to eventually take the set 6-1. She dictated terms with powerful groundstrokes as Andreescu, in her eighth match in nine days, ran out of gas.
Joe Flacco To Fans: "Can’t Imagine A Better 11 Years"
The last time the Chargers played New England in the postseason, they lost 21-12 on January 13, 2008, at Gillette Stadium. The 37-year-old Rivers, like Tom Brady , continues to defy his age in his 15th National Football League season.