The Russian had four quad jumps scheduled for her free skate but fell on her opening quad flip in the Skating Club of Boston in Harwood, Massachusetts.
Undeterred, the 17-year-old landed a quad Salchow but then underrotated and had a hand down on a quad Lutz before a sketchy quad Lutz-Euler-triple Salchow combination.
However, her high technical elements score was enough to secure her victory in the free skate with 142.05, and a winning total of 216.80.
Fireworks had been expected after the two-time world junior champion landed no fewer than five quad jumps at last weekend's Russian test skates.
And while her execution was somewhat lacking, her array of quads makes her one of the most exciting women in figure skating right now.
For the second day running, Korea's Park Yeonjeong pushed Trusova surprisingly close as she marked herself out as a star of the future.
On her senior international debut, the 15-year-old from Seoul landed seven triple jumps as she posted a career-high 141.33 in the free skate, an improvement of 19 points from her previous best.
That gave her a total of 212.40, a mark which would have been good enough for fourth at March's World Championships.
Third place on the day, and overall, went to home skater Gabriella Izzo who posted a free skate personal best of 118.83 for a total of 182.76.
This was Trusova's first competition since she returned to coach Eteri Tutberidze in May after spending a year with Evgeni Plushenko.
A two-time world junior champion, Trusova won both her Grand Prix assignments in her debut senior season but had to settle for third place behind training partners Alena Kostornaia and Anna Shcherbakova at both the Grand Prix Final and European Championships.
Kostornaia followed Trusova to Plushenko's training setup, but has also since returned to Tutberidze's Sambo-70 club in Moscow.
The Americans led after Friday's rhythm dance and, apart from some below-par twizzles, looked impressive in the free dance. They received high grade of execution scores in their 123.24 for a winning total of 207.30.
Diana Davis, the daughter of coach Tutberidze, and Gleb Smolkin were second thanks to a 115.42, their second big personal best in consecutive days. Their total of 190.63 was some 25 points higher than their previous best overall tally.
Third place went to Eva Pate and Logan Bye of the United States as they moved up from fourth overnight thanks to a 104.50 in the free which gave them an aggregate score of 171.70.
The Canadian duo scored 125.62 in their free dance for a winning total of 208.97.
Spain's Olivia Smart and Adrian Diaz took second with 191.31, ahead of Caroline Green and Michael Parsons of the United States (188.43).