Laulauga Tausaga obliterated her personal best by over four metres to take a world discus gold just as rival Valarie Allman had been cruising towards the title.
Tausaga is of Samoan heritage and was born in Hawaii.
Tausaga, who finished last in the previous two world finals, came into the showdown with a best of 65.46 metres but found 69.49 with her fifth throw, before sprinting into the crowd to celebrate with her supporters.
Olympic champion Allman owned the top six throws of the season, the best of them almost three metres better than anyone else in the field.
Tausaga said afterwards she doesn't know if she has a fairy godmother or her ancestors had some say in her surprise success.
Ancestors assisting
"I don't know if I have a fairy godmother or my ancestors had some say in it, but I was able to do something tonight that I didn't think was possible," Tausaga said.
"I was confident if I was on my A-game I could sneak through into a medal place and not be 12th like I was in the last two world championships.
"It's unbelievable to go from 12th to first. I just said to myself, 'You need to let it out and if it fouls, then so be it'. But it sailed out to that big throw and here I am.
"I have a gold medal, I can't believe it, it's so unreal. When I saw my distance I just couldn't get to my coach fast enough to give him the strongest hug of my life."
Reuters reports Allman had a face like thunder at the end and said: "I wanted to be the champion tonight, it is not a secret.
"I have been training very hard, putting everything in for the victory. It's tough when you are in a good form and you cannot reach the gold medal.
"But I feel so proud of being on the podium and a one-two for USA is also so special, to stand together with Laulauga."
Rose makes final
American-based Samoan Alex Rose made the final of the men's discus in the Hungarian capital just 24 hours earlier.
Rose had thrown a massive 65.26 to qualify comfortably for the final.
However, his first two throws were not recorded and his third and final throw of 61.89 was not enough to make the final eight and he finished 12th of 12 competitors.
The 31-year-old is based at West Branch in Michigan.
The multi-times winner of the Oceania Championships had finished a respectable 8th at the 2021 World Championships in Eugene, Oregon.