United States head coach Bruce Arena said action should have been taken after two El Salvador players appeared to bite two of his side.
Striker Jozy Altidore seemed to be bitten by Henry Romero and defender Omar Gonzalez by Darwin Ceren in a similar incident during the Gold Cup quarter-final, which the US won 2-0.
“There should have been a player sent off tonight,” Arena said.
“I didn’t see the play live, I can’t fault the referee.”
The Confederation of North, Central American and Caribbean Association Football told BBC Sport it was “aware of the incidents” and an investigation was under way “to assess whether a disciplinary process is warranted”.
Uruguay’s Luis Suarez was banned from all football-related activity for four months and suspended for nine international matches after being found guilty of biting for the third time in his career at the 2014 World Cup.
He was banned for 10 games for biting Chelsea’s Branislav Ivanovic during a Premier League match for Liverpool in 2013 and was also suspended for seven games for biting PSV Eindhoven’s Otman Bakkal while playing for Ajax in 2010.