It took a Raul Jimenez penalty in extra-time to clinch Mexico's place in the final at Haiti's expense, and Theiler – in control of the team in the absence of suspended coach Gerardo Martino – said the Wolves striker was indebted to El Tri's fans for driving him on.
Mexico will face either the United States or Jamaica in the final in Chicago on Sunday, and Theiler said Martino will demand another high-intensity performance from his players.
"The people of Mexico in all stadiums is admirable. We draw attention because the amount of people who fill the stadiums and the fervour they give to the games," Theiler told reporters.
"This gives the players extra incentive; Raul seemed tired for a moment, but he reinvented himself and was still running at the end and that is what the fans who are supporting, screaming and encouraging want us to do.
"It has been a nice surprise, and it does not happen in all parts of the world - it happens in the United States and Mexico."
Jimenez's goal was the 15th in five Gold Cup matches for Mexico, who have seen off the challenge of Cuba, Canada, Martinique and Costa Rica as well as Haiti.
Martino will take the reins in Sunday's final, where Mexico hope to lift the Gold Cup for a record 11th time but will first have to overcome either holders USA or 2017 runners-up Jamaica.
"From here to Sunday's game there will be a lot of rest," said Theiler.
"We have five days to limit the amount of wear and tear that comes with training, so there will be many videos, talks and correcting the things we have done wrong today and strengthening all the good things we did.
"The intention is for the boys to arrive well for Sunday's final. The intensity of the matches is great, because Gerardo Martino's style is constant pressure and attack and that is why the players are worn out.
"The objective is to arrive in good condition on Sunday, so that the team can perform at their best."