There is definitely a difference when a player plays for a club and when a player plays for his country, and in matches and meetings the players are closer, and also play more in the club than the national team. And also can make a solid team and also understand each other's game.
and what i see with Messi when he plays for club and country has differences like lack of enthusiasm and also not good unlike at his club due to some factors, limited meetings and training and also there must be some players who are weak and this must be experienced by all country. In contrast to players who have the spirit of nationalism they will continue to play very well and defend their country.
Much depends on the status of the tournament. As the Nations Cup has shown, even star teams like France or England can act like they don't care at all about the outcome of games if the tournament isn't important.
As for Messi, in the last year in the national team, he looked better than in the club. Perhaps the environment (Barcelona) played a key role in his achievements. But football is a team game, so one cannot be completely sure of such conclusions.