The Eastern Orthodox Churches have, here in the American diaspora, a situation of overlapping jurisdictions. It is the same for Eastern Catholic Churches.
Generally, EOCs align along national boundaries and the bishops of a particular church are charged with the care of the faithful in that church’s home country. When Europeans emigrated to the United States, they did not immediately found an American Orthodox Church, but they recognized their jurisdictions from back home.
Therefore, we have Russian Orthodox bishops who care for dioceses here, overlaid with Greek Orthodox bishops’ jurisdictions and (arch)dioceses. We also have phenomena such as ROCOR and OCA. OCA was actually born of a schism of Byzantine Catholics who were treated poorly by Latin bishops. The existence of OCA does not obviate the perceived need for other Orthodox jurisdictions.
Continuing on, we have Serbian Orthodox, Antiochan Orthodox, and so on and so forth. It is, admittedly, very inefficient, and not how governance was envisioned in the Old Country.
Many Eastern Orthodox faithful are quite content to drift back and forth between parishes and jurisdictions based on their preference. Naturally there is much intercommunion practiced. Even with the Hellenic/Russian schism active, on the ground that is not a big deal for many Americans.