Mbappé opened the scoring in the fourteenth minute at Lincoln Financial Field, cutting inside from the right to receive Michael Olise's pass and unleashing a powerful strike from the edge of the penalty area that beat goalkeeper Ahmed Basil at his near post.
France were in control at the interval when a violent thunderstorm forced both teams from the pitch. What followed was a two-hour and fifteen-minute delay, the first weather stoppage of this kind in World Cup history.
When the players re-emerged, the pitch was waterlogged and required extensive work from ground staff before the game could resume — a situation that prompted a visible reaction from France captain Mbappé, who was seen remonstrating with the referee and match officials during the clean-up.
He explained his frustration after the game.
"It wasn't annoyance. It's just that the part of the pitch where we were attacking was completely waterlogged but they spent twenty minutes cleaning the part where we were defending, not the other one.
"That was a disadvantage and I wanted them to spend the same amount of time cleaning both halves. Or, if anything, clean the half where we attack so the other side slows down too. But it wasn't their fault — they were told to go there and the other group wasn't ready."
Once play resumed, Iraq conceded a second when a dreadful mix-up between Basil and a defender gifted Mbappé a simple finish. Ousmane Dembélé added a third — his first World Cup goal — to seal a comfortable victory.
France head coach Didier Deschamps put the result in context.
"In the second half, we were completely in control, bearing in mind that it wasn't straightforward given what had happened. But putting the result beyond doubt is a very good thing; we've qualified tonight, even though I'm convinced that the third match against Norway will be decisive for our final position in the group."
Left-back Lucas Digne was equally positive.
"It's another step forward for us. We know what we came here for; we'll keep working match by match and keep improving. I really enjoyed this match — we won 3-0 and kept a clean sheet; it's been a perfect evening. I felt good; my team-mates and I know each other well."
Mbappé's sixteen career World Cup goals draw level with Klose's record, which stood for twelve years, though Lionel Messi — who scored twice earlier in the day against Austria — now leads the all-time standings with eighteen. France top Group I ahead of a decisive final group match against Norway in Boston on June 26.