Nationalities in football

It is kind of annoying to be a fan of a sport where old-fashioned nationalism thrives: football.

I was just reading an article about Arsenal's Spanish goalkeeper Manuel Almunia, who after many years in England, is planning to become an English citizen. Since he has never played for his native Spain, this would make him eligible for the English national team (who does have a goalkeeping problem).
Why does this seem to annoy so many people? Examples are so numerous, historically and in football, about the fluidity of nationality, as to make the arguments about football nationality irrelevant, particularly in Spain, who continues to sport non-Spanish born players on its national team, Senna, as well as having done it before: Di Stefano, Puzkas, Donato...
France has a long list of players born in Africa, and Germany has quite a number of players of mixed nationality. Turkey has players who were born, raised and live abroad, while even the Italian defending champions had one on their team, besides having Christian Vieri, whose brother in fact plays for Australia.
Portugal has many Brazilians, besides their big star Deco, as well as having had their greatest star, Eusebio.

In none of these teams, does anybody doubt the nationality of any of the players, and none of the players make any of these teams less "national". In fact, I would even argue that it makes them more so, as it opens up for the changing and evolving cultural structures in national societies, where it is constantly re-defined what it means to be "from somewhere". Football-players like these are important contributors to this.
For many people, and in some countries, nationality is something about the blood or whatever undefineable. I saw a thing on Danish TV3 not long ago about how Zlatan Ibrahimovic would never have had a chance to make it to the national team in Denmark, while in neighboring Sweden he did have the support to become a great Danish star. And this tells you more about Danish society than it does about the football players or the national football team!

Let us forget this, and enjoy football as it is: in truth, the best football is seen in the multi-national club teams of the Champions League, rather than in second-rate national teams that assemble but twice a year. Still, "normal" people (that is, not football-fans) tend to like the latter because it appeals to the lowest common denominators of national tribalism.