Mbappe damaged his nose in the team's first game of the tournament and although he missed only one match, the injury, and mask he had to wear clearly had an impact on his performances as France failed to impress despite reaching the semi-finals.
Now at Real Madrid after seven seasons with Paris St Germain, his enthusiasm has returned, and he scored to help the club win the UEFA Super Cup and netted twice in Sunday's 2-0 win over Real Betis.
"In Madrid, it's going very well, we've already won a trophy. It's getting better and better in terms of performance, I've scored goals, now I'm focused on the national team," Mbappe told a press conference before France host Italy on Friday.
"My nose is no longer broken, so it's already better than at the European Championship. I had tests at Real Madrid and they told me that it was not necessary to have surgery, I can breathe and sleep well.
"I feel good. Physically, mentally, I'm fine. I am happy."
The Nations League may not hold the same appeal as the Euros, but Mbappe knows the difference between doing well and faring badly in this competition, which France won in 2021 before finishing third in their group a year later.
"For us, there is nothing more important than the French national team, we have already won this competition and there wasn't an extraordinary reaction," Mbappe said.
"We won in Milan (the final against Spain) and at the end of the game, I didn't even feel like I had won a trophy. But, when we lost it, it was the end of the world."
Mbappe and France faced plenty of criticism after the Euros, but he has learned to ignore the opinions of others.
"I'm at a point in my life and career where I don't think too much about other people's evaluations," he said.
"I arrive, play and always try to give my best, the best possible version for the national team. I love this shirt. Then in football, you can't satisfy everyone."
Along with Italy, France will also face Belgium and Israel in their Nations League group, and manager Didier Deschamps is keen to use the competition to try out new players.
"To make steps forward we need to see the players in action and these six games will be useful to many players," Deschamps said.
"Through this Nations League, it is in my opinion necessary to see the greatest number of players."
