Just watch these two teams play (Argentina and France), and it is very evident. I have never noticed anyone in Argentine squad playing selfishly. They readily pass the ball, depending on the situation and circumstances. But with France, I have noticed several times that their players waste golden opportunities to score, just because they don't want to pass the ball and try to score the goal by themselves. France maybe having some of the best players in the world. But nothing can be done if the players don't trust each other.
It's true what you said, in fact most of the players in the French National Team are naturalized from other countries. Personally, the egoism that is shown is not based on the origin of the player but rather on his star status at club level and individual fan base. The role of the coach and seniority is very important to reduce the attitude of fellow players on the field so that the final goal is to win the match. Didier Deschamps' squad in the Euro 2024 qualifiers was mostly made up of young players overall, otherwise only Giroud and Griezmann are over 30+.
Specifically, I would say that a player who is selfish above the average other players in the French squad is Mbappe, yes, I think it's natural because he is the main focus of the team. Maybe he will become a permanent captain to replace the role of Hugo Lloris who retired from the national team.