Geographically, the two churches were separated from each other.  In addition, because of this there were great cultural differences as well.  There was also a power struggle where Rome claimed the right of power.  Also part of this contributed to a lot of political tension in the west and in the east they focused a whole lot more on theology.  Part of this as well was a disagreement on what the priests would wear as well.  With icons, the east used a whole lot of them and the west hardly used them at all.  The west had a very high view of the pope as the head of the church but the east denied he was infallible.  Last, the east was not tied to just one city but it had a lot to do with similar worship, bishops and early councils in the east.