Hayes, who had five goals in helping the Americans to the CONCACAF championship in March, tallied in the 50th, 74th and 92nd minutes to lead the United States to its 14th win in 16 group matches at the U-20 Women's World Cup.
One of the two games the United States did not win was a 1-1 draw with Ghana to open the 2010 U-20 women's finals in Germany.
The Americans went ahead in the 20th minute when Morgan Brian headed Vanessa DiBernardo's corner kick off the crossbar. The rebound struck Ghana defender Linda Addai and bounced into the net for an own-goal.
Hayes doubled the lead by heading in Kealia Ohai's cross, added her second off a flicked header from second-half substitute Samantha Mewis and completed the scoring by chipping over the head of Ghanaian keeper Patrica Mantley.
The victory was the United States' 13th this year with one draw.
It will next play China on Thursday before finishing its Group D schedule against defending champion Germany.