Gianluca Busio put the United States ahead in the third minute but Senegal rallied for a 4-1 victory over the Americans in its opener at the Under-17 World Cup on Sunday in Cariacica, Brazil.
Busio scored on a header off a cross from Joe Scally.
Senegal got goals from Souleymane Faye in the third minute of first-half stoppage time, Aliou Balde in the 72nd, Amete Faye in the 76th and Pape Saar in the 88th.
Tayvon Gray's volley off a pass from Gio Reyna was saved off the line by defender Birame Diaw 10 minutes into the second half.
Gray received a red card in the 87th minute when he fouled Souleymane Faye to prevent the forward from breaking in along on goalkeeper Damian Las.
The U.S. plays Japan on Wednesday, then closes Group D against the Netherlands on Saturday.