Goalkeeper Nicole Barnhart, starting for the injured Jill Loyden, made a save to spark a counterattack that forward Sydney Leroux finished off in the 14th minute.
Defender Ali Krieger doubled the lead in the 32nd by scoring her first international goal from a cross by Alex Morgan.
The U.S. extended its unbeaten run over China to 21 straight games when China's Wu Haiyen scored an own goal in the 47th before Christen Press and Whitney Engen added two more.
The Americans face former coach Pia Sundhage when they play Sweden on Monday in the final match of the group phase.
More Sports Headlines
Seahawks' Wilson, who has been sacked 161 times, keeps getting up Bengals’ passing game will test Seahawks’ secondary Seahawks vs. Bengals at a glance Laurencelle goal in OT lifts Silvertips to 5-4 win over Chiefs Cougars upset Oregon 45-38 in double overtime Is the Seahawks' ship really back on course? No. 5 Utah intercepts 5 passes, beats No. 23 California 30-24 Utley's slide helps Dodgers beat Mets 5-2, tie NL division series 1-1
Our new comment system is not supported in IE 7. Please upgrade your browser here.