The only person Bianca Andreescu didn't shock with her US Open win? Herself

Andreescu: I'm beyond grateful and truly blessed (1:19)

Bianca Andreescu reacts to becoming the first ever Canadian Grand Slam champion and calls her opponent Serena Williams a "true legend of the sport." (1:19)

NEW YORK -- Earlier this week, Bianca Andreescu told the media that as a 15-year-old, she wrote herself a fake check in the amount of the prize money of the US Open. She still has it, but she can now replace it with the real thing.

On Saturday at Arthur Ashe, where some fans were still struggling to pronounce her name, the 19-year-old won the US Open title, 6-3, 7-5, to become the first Canadian to win a major. And Andreescu did it by beating Serena Williams, in her latest attempt at winning her record-tying 24th Grand Slam title.

After hitting a forehand winner to seal the victory, Andreescu dropped her racket and put her hands on her head in disbelief -- as she had many times over the past two weeks. She and Williams hugged warmly at the net, then she dropped to her knees on the court, kissed it, rolled over on her back and soaked it all in.

"I've been dreaming of this moment for the longest time," she said while the tears started to roll down her face. "After I won the Orange Bowl [as a 15-year old in 2015], a couple months after, I really believed that I could be at this stage. Since then, honestly I've been visualizing it almost every single day.

"For it to become a reality is just so crazy. I guess these visualizations really, really work."

Prime Minister Justin Trudeau was just one of countless Canadians to celebrate her monumental victory on Twitter. The hashtag, #SheTheNorth, in reference to the Toronto Raptors' catchphrase, was instantly trending worldwide. Andreescu had come to New York a player to watch, and is leaving as tennis' next superstar and Williams' new heir apparent.

Few had expected her to reach the final in her main draw debut in Queens, despite a breakthrough season. She herself seemed shocked after her semifinal win over Belinda Bencic. After the match she had talked excitedly about facing Williams, but did not seem scared. "Hopefully, I guess, may the best player win," she said matter-of-factly.

On Saturday, Andreescu left little doubt who the best player that day was. With a powerful serve and equally strong returns, she played the type of game Williams is known for. She had four aces in the first set to seemingly stun her far more experienced opponent, and 19 winners on the day. She said her game plan was simply to make Williams work for every ball, and get as many returns in the court as possible. She was happy it worked, and felt Williams was "intimidated" from the very first game.

While she was complimentary of Andreescu's play, Williams was adamant she didn't play her best tennis and seemed to think the final result had more to do with her failures than Andreescu's successes. "I felt like I could have done so many things a little bit better," she said afterward. "But she played really well, and she deserves this championship.

"I love Bianca. I think she's a great girl. But I think this was the worst match I've played all tournament. It's hard to know that you could do better. It's just taking it, whatever. I don't even know what to say."

It's been an incredible season for Andreescu. After failing to advance out of the first round of qualifying at the 2018 US Open, she finished the year ranked No. 178 in the world. She was home in Ontario while Williams and Naomi Osaka were battling for the trophy in Queens. "I was injured and sitting on my butt," she said when remembering it.

She went to Auckland to start the 2019 season hoping to qualify for the main draw. After three wins in qualifying, she stunned top-seeded Caroline Wozniacki, then the rest of the field, by making it to the final. That tournament was the moment, she says, that started it all for her, and made her believe she could beat the best players in the world.

The confidence propelled her to another run at Indian Wells, her first premier tournament, where she topped three-time Grand Slam champion Angelique Kerber for the title. She then missed most of the next several months due to a right shoulder injury, but returned in time for her hometown tournament at Toronto.

She faced Williams in the championship match there too. She held a 3-1 lead before Williams retired with a back injury. The two had an instantly viral moment following the match's conclusion, with Andreescu comforting a teary Williams. Williams later said she was "officially a fan" -- and it was clear she still felt that way on Saturday.

"Bianca played an unbelievable match," Williams said on the court after the match. "I'm so proud and happy for you. It was incredible tennis out there, but if anyone could win this tournament -- outside of Venus -- I'm happy it's Bianca."

Andreescu hasn't lost a match since the semifinals at the Mexican Open in March. She retired from both Miami and the French Open due to injury, but hasn't actually been defeated since a three-setter against Sofia Kenin on March 1. She will become the fifth-ranked player in the world on Monday.

Unlike Osaka, the 2018 champion, who seemed initially apprehensive of her new star status, Andreescu seemed more than ready for her moment. She seemed very much at ease with her new life on Saturday night. She said she hadn't thought too much about fame, but also admitted to enjoying the attention.

"I never really thought about being famous," she said. "My goals have been to just win as many Grand Slams as possible, become No. 1 in the world. But the idea of fame never really crossed my mind.

"I'm not complaining, though. It's been a crazy ride this year. I can definitely get used to this feeling."

It was as if she hadn't just visualized winning the title, but everything that came after as well. Following Andreescu's news conference, her coach, Sylvain Bruneau, was presented with a trophy of his own. He joked he wasn't used to getting such a thing. Andreescu didn't miss a beat. Through a perfect smile plastered on her face for the photographers, she said authoritatively, "Get used to it."

The room laughed. But it was clear she was serious. When talking about her admiration for Williams, she casually added a caveat at the end.

"I've really strived to be like her," she said. "Who knows? Maybe I can be even better."