Warner started an altercation with Root in the Walkabout bar on Broad Street in the early hours of June 9 with the two players among a group of members from both teams who were in the bar following England's 48-run Champions Trophy win over their old rivals at Edgbaston.
Collier said: "There were some very, very good things that did come out of it in terms of the relationships between the two sides."
Root did not respond to Warner's provocation, which has since seen the 26-year-old both suspended until the first Ashes Test on July 10 and fined £7,000.
Cricket Australia (CA) dealt with the situation swiftly and lambasted Warner for his behaviour and Collier revealed that both bodies were in unison in reprimanding the actions of Warner.
"Clearly we don't condone that kind of incident, I think Cricket Australia dealt with it very well," he said.
"The headlines were very different, I can tell you behind the scenes there were some very good discussions between the two teams as a result in terms of positive relationships and agreements that it is not the way we want the series to go.
"It is past us now, there are some lessons that have to be learnt and that have been learnt."
With Warner missing for their remaining two group matches, Australia were eliminated from the ongoing Champions Trophy tournament and the former Durham player will also miss tour matches against Somerset and Worcestershire before the first Ashes Test at Trent Bridge.
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