The U.S. beat Japan 86-69 on July 30, three days after beating Nigeria by nine in the opener, according to ESPN.com.
That was the first time a team had come within single digits of the U.S. team in the Olympics since 2004.
While the U.S. has now won 51 consecutive games dating back to the bronze-medal game in the 1992 Olympics, the 13-point average margin of victory in the first two games in Japan is far below that of the previous six Olympics in which the Americans ran through teams.
"This tournament more than ever feels like a combination of things," five-time Olympian Sue Bird said. "I'm never not going to give credit to other countries for putting out a great product. There's so much talent. I think this tournament for us is unique that we have six newcomers and you can't rush chemistry. ... We're still trying to figure it out."
The U.S. team plays France on Monday, Aug. 2.