Yes. He needs more experience, especially for international matches. It is not only about handling stress, but he needs to improve his chemistry among his national teammates. It is quite different from the League or UCL because he plays with his teammate that spends much time playing together. While for international matches like in Euro or World Cup, they play with different teammates and with a very limited time to play together.
France have a very stable squad in the last 3 tournaments: Euro 2016, World Cup 2018 and Euro 2020 (2021) and their problems are many players in the squad feel like they are on the top of the world and in the Europe. It is their problems and Mbappe has his personal issue that probably contributes by social media. They said he is a next Messi and will compete with a next Ronaldo, Haaland.
When Mbappe can keep his mind and foot unaffected by social media, he will become a legendary player.
Mbappe can be another Thomas Mueller who shined too early in international skirt but in late of career, his contribution has been less and less.
It was really unfortunate for Mbappe. But no player wants to miss a penalty. As a fan, we didn't like it. But at the end of the day, Mbappe is a man, we should not scold him, or humiliate him. He is definitely talented. And in the future, he will be able to give us much good gameplay.
Many super stars missed their penalty. Zico, Baggio, Beckham, Messi, Ronaldo, Trezeguet so it is not the end for Mbappe. He is too young and has 10 years to contribute more for France and win more international titles.