I’ll add that the nearest parish church doesn’t necessarily determine the territorial parish.
Some time ago, I’d reached the point of wondering what my territorial parish is, but I hadn’t reached the point of calling the diocese to ask

, and I long assumed that I live in a certain parish, in part because it has the nearest church.
The diocesan website added a helpful interactive map that shows such things as parish boundaries, and unless something is wildly wrong with this map

, the boundary between parishes turns out to be a short distance from my home. My territorial parish is actually the next one over.
It’s not hard to find similar spots elsewhere on the map, since parish boundaries (at least in this diocese) are not drawn so that the nearest church is always matched to the territorial parish.