I think Kosta answered this well. The Ecumenical Councils determined the territorial jurisdictions of the Patriarchates and forbade 'poaching". Most of the world of course was not known at the time and believe it or not, the Patriarch of Constantinople was given jurisdiction over the "lands of the barbarians", which would surely include us! I don't think we will run into any problems with jurisdictional lines outside of parts of Eastern Europe and perhaps with the Melkites (though I doubt the latter).
But then, at the time of the councils, vast tracts of Western Europe were still 'barbarian lands'. Would the Phillipines then be under the Patriarch of Constantinople?