The gritty Gold Coaster wore down Croatian Petra Marcinko 3-6 7-6 (7-4) 6-3 to finally reach the second round after losing all three of her previous Flushing Meadows openers in 2023, 2024 and 2025.
James Duckworth also advanced on a banner day two for Australian battlers, the inspired veteran notching a mighty four-set upset victory over 2026 French Open semi-finalist Matteo Arnaldi, the men's 30th seed.
But a beaming Birrell stole the day in burying her first-round hoodoo after being forced to return to court 7 following a nervy 14-hour rain delay.
"I woke up around 5am, like wide awake, ready to step out on court and my alarm wasn't for a few more hours," she said.
"So I had to calm myself back down, and try to clear my mind and then managed to get back to sleep."
After surviving a match point in the 12th game of the second set on Sunday (Monday AEST), the 28-year-old was still trailing by a set and a mini break in the second-set tiebreaker before rallying to post one of the most satisfying wins of her career.
Birrell had lost in straight sets to Marcinko on grass at Eastbourne two months ago, having dropped the opening set 6-0 in their first meeting which Birrell won in Texas in February.
"That's crazy," Birrell told AAP after earning a guaranteed pay day of $US190,000 ($A265,000) - or more if she topples Russian world No.19 Ekaterina Alexandrova next up.
Birrell and coach Matt Fraser are wedding planning for their big day in Kingscliff in December and reckon the massive cheque will go nicely on their honeymoon.
"Oh my gosh, I don't think I'll be spending it here," Birrell said.
"I'll definitely save some of it. We're getting married at the end of the year so that helps a lot and maybe I'll buy some extra flowers.
"And we've got a mortgage. Yeah, the mortgage."
Birrell is also slated to soar 16 spots to a career-high world No.55, displacing Talia Gibson as Australia's new No.1.
After climbing to Australian No.2 this year behind only world No.7 Alex de Minaur, Duckworth continued his hot run with a 5-7 6-3 6-2 7-6 (10-8) comeback victory.
The 34-year-old has now finally reached round two at all four grand slams and next faces China's Yibing Wu for a place in the last 32.
Birrell and Duckworth follow WA rising star Taylah Preston in progressing, with three more Australians in action later on Monday (Tuesday AEST).
While Birrell and Duckworth marched on, Aleksandar Vukic was unable to win his own weather-delayed epic against Rei Sakamoto.
Sakamoto was up a break deep in the deciding set when their battle resumed, and the Japanese quickly won six more points on serve, without dropping any, to close out a 6-4 6-7 (5-7) 6-4 3-6 6-4 victory.
Alexei Popyrin, Rinky Hijikata and Maya Joint are also playing for second-round berths on day two at Flushing Meadows.
Popyrin takes on former semi-finalist Grigor Dimitrov, who had to qualify this year after being out injured. Rinky Hijikata also has a tough one against third seed Felix Auger-Aliassime and Joint is up against the much-fancied Liudmila Samsonova.
Sixth-seeded de Minaur opens his title quest on Tuesday (Wednesday AEST) against Italian qualifier Andrea Guerrieri.
15°C