First of all most of the pros come from more developed countries because cs is more of a trend in those places. Until FPL came along, you wouldn't see international lineup teams and the only chance you would go pro would be to reach the top along with 4 of your countrymen. Now in countries like Sweden or Denmark, you can more easily dedicate to games and still make money from welfare and redo your life if you fail to make a career in CS, while in countries like ours, your life is pretty much fucked without proper education + experience in your work field of choice.
However nowadays with big teams picking upcoming talents from Academy Teams and FPL, nationality is irrelevant. Your skill and communication ingame are the only factors which matter in this whole business. No one will not pick you up just cause you're from a certain country, if you're willing to relocate. That's just dumb.