Michelle Vittese and Caitlin van Sickle scored for the Americans, who defeated No. 2 Argentina 2-1 in their Olympic opener on Saturday.
United States goalie Jackie Briggs had six saves and had four saves on the four penalty corners she faced. The crowd chanted, “Jackie! Jackie!” after the match.
The fifth-ranked Americans, who lead Pool B with six points, moved closer to qualifying for the quarterfinals. The top four teams in each six-team pool advance.
The Americans dealt a major blow to Australia. The Hockeyroos dropped their opener to Britain 2-1 on Saturday and now have no points with three pool play matches remaining.