Nagasu, 24, finished the women's free skate portion of the eight-program event in second place with a score of 137.53, setting a new personal best. She had a spectacular performance during her four-minute free skate, which the Southern California native began by landing a triple axel jump.
She is the first American woman to land a triple axel (three-and-a-half rotations) and third women to ever do so at the Winter Games. Tonya Harding and Kimmie Meissner are the only other U.S. skaters to do so in an international competition. Midori Ito and Mao Asada of Japan were the previous two women to land the jump at the Olympics.
"I tripped a couple times going into it because I was so nervous, but to tell myself, 'no, I'm going to go for it, 100 percent and not pull back,' that was really special for me," Nagasu told NBC Sports after her skate.
Her performance was key in Team USA earning a medal and gaining separation from the Italians in the standings. The U.S. finished with a score of 62 in the team event, six more points than Italy. Canada won the gold while the Olympic Athletes from Russia picked up the silver.
From Arcadia, California, Nagasu is currently studying international business at the University of Colorado-Colorado Springs, which is near the U.S. Olympic Training Center.
Nagasu is at her second Olympics after she placed fourth in the ladies individual event at the 2010 Winter Games in Vancouver, British Columbia, at the age of 16.
A seven-time U.S. national medalist, Mirai won gold in 2008 to become the second youngest skater since Tara Lipinski in 1997 to win the championship. She won a silver medal at the U.S. Figure Skating Championships in San Jose, California, in January to help her earn the Olympic berth.