The reigning champions and world number one, who had never placed lower than third at a Women’s World Cup, triumphed after two second-half goals.
Golden Ball winner Megan Rapinoe opened the scoring from the spot in the 61st minute after the video assistant referee intervened to award USA a penalty.
Eight minutes later Rose Lavelle added a second to seal the victory in front of almost 58,000 fans.
“It’s surreal,” Rapinoe said. “I don’t know how to feel. It’s ridiculous.”
US boss Jill Ellis became the first-ever coach to win back-to-back Women’s World Cup titles, while 12 members from that squad in 2015 were part of this team.
“They put their heart and soul into this journey, and I can’t thank them enough,” Ellis said.
Meanwhile, Sweden defeated England 2-1 on Saturday to claim third place.