Two-time Australian Open champion Sabalenka was in control from the outset on a sweltering day in New York.
Bronzetti held her own early on, but ultimately the power of Sabalenka was too much for the world number 76.
The Australian Open champion snatched her only break opportunity of the first set to go up 4-2 and calmly saw it out from there.
She promptly broke twice early in the second set and again to secure victory, finishing the match with an impressive 24 winners.
“I told myself that I had to stay focused from the first point to the last one, and make sure you’re not going to spend a crazy amount of hours [playing] so you’re ready for the next one,” she said.
“It’s tough conditions to play in but I’m happy I was able to manage the win in two sets.”
Defending champion Coco Gauff, who beat Sabalenka in last year’s final, is in action in the night session at Flushing Meadows.
