Hector Moreno scored in added time to earn a point for the Mexicans five minutes after Cedric put the Portuguese in front.
"It wasn't the result that we wanted," said Ronaldo. "There's no need to set off any alarms, the team was good. It was a good result at 2-1 but that's football. They scored in the last few minutes and now we think of the next game.
"We need to keep believing in ourselves, we know we have a great chance. There are two games to go and that's why we're cool, we're at ease. Now we need to think of the next game, which we have to win. If we win we're one step away."
Portugal play hosts Russia in Moscow on Wednesday, while Mexico take on New Zealand in Sochi. The Russians top Group A after beating the All Whites 2-0 on Saturday.
The FIFA Player of the Year, who had scored 11 goals in seven games coming into Sunday’s encounter, was perhaps not as influential as usual but was still named man-of-the-match.
The Real Madrid striker, whose club future has been the subject of media speculation after he was accused by Spanish prosecutors of committing tax fraud, which Ronaldo denies, set up Portugal's opener.
His pass split the Mexican defence and gave Ricardo Quaresma a golden opportunity to open the scoring.
Ronaldo was also involved in one of the game's biggest talking points, a 'goal' that was disallowed after consultation with the Video Assistant Referees.
His 30-metre strike bounced off the bar and Nani hammered the ball home but the referees disallowed the effort for an offside infringement earlier in the move.
Mexico striker Javier Hernandez cancelled out Quaresma's opener shortly before halftime and the two goals in an exciting last six minutes ensured the teams shared the points.
The result preserves an important run for each side.
Mexico's last competitive loss came nine games and exactly one year ago when Chile hammered them 7-0 in the Centenary Copa America.
Portugal, meanwhile, kept up their unbeaten run against the Mexicans and took their record to two wins and two defeats in the four matches contested from their first meeting in 1969.
"We played a team that has very good, technical players," said Portugal coach Fernando Santos.
"At the start we couldn't enjoy good control of the ball but then we managed to balance things out and could have won it... In the end the result was fair as Mexico also played well."