Together with Jelena, I wrote a blogpost on citizenship and football published on the observatory on citizenship I work for. We did some research and found out that 220 players at the world cup, that is one out of three, have dual citizenship. These include the likes of Lionel Messi (citizen of Spain and Argentina), Kylian Mbappé (France, Cameroon and Algeria), Dele Alli (Nigeria and England). These players could well be representing another national team, if they had made the choice. And so could other players in the past: imagine what previous world championships would have looked like if Patrick Viera had chosen to play for Senegal instead of France, John Barnes for Jamaica instead of England, Miroslav Klose and Lukas Podolski for Poland instead of Germany. You can see the visualisation we have made following this link and you can read the article here.
Post scriptum, July 23 2018: we have now published an updated version of this post on the nccr – on the move blog.