Hypothesis: Your country's likelihood of fielding a world-class soccer team is roughly proportional to the number of person-days of access that the average kid has to an unfrozen soccer field.
Isn't this like asking why US colleges north of, say, Virginia have so much trouble recruiting top-class college baseball players, such that the College World Series always seems to be "some team from Florida vs some team from Arizona"? Aspiring players of professional baseball prefer to play for teams whose home field thaws out before April.
Of course, the opposite is also true. Great hockey players are more likely to be hail from Russia, Canada, New York, or Massachusetts than from Brazil, Italy, London, or California.
Honestly, I don't understand a point of professional team sports at all. If every team of every country can in principle hire every player from every country, constrained mainly by its budget and negotiating abilities - it becomes mainly a battle of budget, and politics also.
