On the subject of the French national team. France used to be a colonial power. That's why there are more people of African descent in the country than in other countries. It is true that they are over-represented in the national team, but it is a fact that black people are usually better athletes and coaches will always just the best players that are available to them.
It means why would you pick that nations team and why would that nation accept you, but for some reason both players and those nations fall in love with each other and sometimes even become bigger than the players from that nation because the outsider wants to prove that they really want to and work really hard versus the player who was already born there and do not care about the result.