Barcelona captain Iniesta was in mesmerising form once again in Nice on Friday as he helped inspire the double-defending champions to a comprehensive victory.
Alvaro Morata opened the scoring with a superb header in the 34th minute, before Nolito added a second shortly after.
Juventus forward Morata then made it three after half-time when he rounded off a brilliant team move, and man of the match Iniesta was delighted with Spain's dominant display.
"We have to keep growing as the tournament goes us and minimise our mistakes - and that is what we did today," Iniesta said at a post-match news conference.
"We had a difficult opponent, but we had a lot of possession and kept on getting better. I would give the players a 10 out of 10, and the fans as well.
"The World Cup was disappointing for everyone, for the players and for the fans. We never expected we would have such a tournament, but we have responded in these past two games and shown our winning mentality. We have positive feelings and it is in our own hands how far we go."
Iniesta also had his say on the situation of his Barcelona team-mate and Turkey star Arda Turan, who was booed by his own fans in the second half.
"It's a difficult situation for a player to experience something like this, being whistled by your own fans," he added.
"It leaves a bad taste in my mouth for Arda. He is a great player with a lot of quality.
"I wished him the best for the remainder of the tournament. I always want the best for my team-mates."