Croatia's 2-2 draw with Czech Republic was marred by a small number of fans throwing flares on to the pitch as a form of protest against the Croatian Football Federation (HNS).
As part of UEFA sanctions, the HNS have also been told they will be banned from selling tickets to fans identified as hooligans if there is any further trouble during Euro 2016.
However, Cacic is hopeful this will not be the case and wants the recent adversity to have a galvanising effect.
"I'm not too worried," he said. "I think the organisers and the French police can be more prepared and try to fix all these problems.
"I think our supporters are going to be much better. We have to be focused on what is going on on the pitch and try to play our best.
"We have a really good group of players. They are behaving like a family and promoting Croatian football and the Croatian nation.
"Everything that is going on with the supporters, all these problems are making us stronger.
"You can trust that we will fight until the very last moment."
Cacic added: "I have some good news - that no one can terrorise a whole country while our team are playing in such a perfect way. They are representing our nation.
"The supporters were behaving really well in the town and at the ground was the only time when they caused some problems."
Midfielder Ivan Perisic, who opened the scoring as Croatia dazzled for much of the match in Saint-Etienne, also backed his team-mates and supporters to turn around a trying few days.
"It was not easy after the match against Czech Republic but the feelings are now much better and the atmosphere in the team is perfect," he said.
"We played really well against Turkey and the last 15 minutes against Czech Republic were not good. We conceded two goals and we should not repeat these kind of difficulties."
He added: "Of course we are expecting really great support from our supporters as in the first two matches, like it was before this incident
"We really hope our supporters will be at their best, like we are used to, because we really need them against Spain."