The Church, because of the difficulty of travel and the impossibility of one man knowing all of the inner workings of each particular church, had these rules:
- Bishops were elected by the other nearby bishops, and ordained by them (to maintain Apostolic Succession)
- The bishops of the metropolises could either approve or reject the man chosen
So, as you can see, Rome oversaw the appointment of bishops in Western Europe, but also Northern Africa I believe. Alexandria oversaw Egypt, Libya, Ethiopia, and the rest of Africa. Jerusalem oversaw what is roughly modern-day Palestine, and Antioch oversaw Asia Minor, Eastern Europe, Syria, and all the east. Of course, the Church grew so rapidly eastward that minor metropolitans were created out of necessity, like the Catholocoi of Armenia and India, although these were subject to the oversight of Antioch.
Hence, seeing as the vast majority of the modern Church is Latin, it is only fitting that the areas that come under Latin jurisdiction should have their bishops appointed by the Pope, who is the Patriarch of the West (and All the Americas - I think he should add that title.

- the American Orthodox would be hopping mad).