Why do many South American players who play in European clubs have dual nationality?

The first is the second nationality of the country and the players. National laws allow many nationalities, and many players are immigrants from other countries. For example, many Argentine players are actually descendants of Italian immigrants! The most important factor is that if an American player has European nationality (especially the nationality of a country that has joined the European Union), he does not have to occupy a valuable position of non-European and American players in European clubs. For example, Serie A seems to only allow two non-European players now, but look at Inter Milan and Argentina helping AC Brazil, which is the advantage of dual nationality.