johnnydawg68
Chairperson, People's Front of Saint Domingo

http://www.economist.com/blogs/dailychart/2011/01/european_football
Interesting chart here. France and Spain have the highest % of domestic players in their top flight leagues, and France is the highest exporter of players within Europe. Brazil is the highest overall.
Considering the success at the international level these 3 nations have had recently (albeit not at the same time in the case of France and Spain), it could be argued that the key to a successful international team is 1) have a high % of your domestic league be populated by domestic players, and then 2) Export a certain amount of them to other European leagues.