The debris can't actually be in a geosynchronous orbit
If it was, it would maintain the same relative position over the Earth, just like GSO satellites do. OK, it isn't exactly fixed since the Earth isn't exactly a sphere, they do little figure 8s over a range of a few miles. But if there is debris at say 90W it would only ever potentially affect satellites assigned to 90W and even then only if their figure 8 bounding boxes overlapped.
Only debris in a somewhat elliptical orbit so it can cross the GSO plane in different spots is of true concern, since it could potentially affect any satellite over any spot in the world if it happens to cross the GSO plane at the wrong time.