"Last year wasn't an easy period in my life, I was going through a lot with injuries," said Andreescu.
"I just kept believing in myself I kept working hard and I just kept that momentum and confidence.
I know you guys wanted Serena to win – I’m so sorry!
"It's so hard to explain (what the win means) in words. I'm just beyond grateful and truly blessed. I've worked really, really hard for this moment and I can't complain. This year has been a dream come true.
"And now to be able to play on this stage against Serena, a true legend of the sport, is amazing."
Dropping only two sets in the entire tournament, the tenacious, power-hitting Andreescu barrelled through the competition at Flushing Meadows, showing no sign of a slowdown from a blockbuster summer that included wins at Toronto and Indian Wells.
Ending 2018 with a year-end ranking of 178, she had rocketed to 15th when she arrived at the year's final major, a meteoric rise that stunned even her coach.
Her surge into the game's elite culminated on Saturday with a 6-3 7-5 victory over 23-times Grand Slam singles champion Serena Williams.
Image credit: Getty Images
And the young upstart said she is not planning on slowing down any time soon.
"I love this feeling way too much," Andreescu said in a televised interview after the match, as her loyal Canadian fanbase cheered behind her on the plaza outside Arthur Ashe Stadium.
"I'm really looking forward to what I can do in many years to come."
In defeat, a gracious Williams, who has been beaten in four Slam finals since claiming her last major title at the Australian Open in 2017, was prevented from equalling Margaret Court's record of 24.
"Bianca played an unbelievable match," she said.
"Congratulations, I'm so proud and happy for you. I wish I could have played better."