First of all I'm sorry for my bad English.
Indeed it's very idiomatic, but this expression is still used by journalists and press. Actually, it comes from the fact that in France, the church was the main symbol of the village (or the city...). Literally, that would mean "My village is better than yours", "My idea is better than yours", all in the case where all those things are very close.
So, today when someone says "c'est un querelle de clocher (ou de chapelle)" it means that it's a quarrel about something frivolous, with a very local impact, either because it's really the case or because someone wants you believe it.
Another way for saying it: "Un orage dans un verre d'eau" (literally "a thunderstorm in a glass of water")
This kind of parochial bickering should stop so that we can
continue to build what truly is recognized around the world as a great
country in which to live....
Is the Mount Saint-Michel in French Britannia or in Normandy?
Is Haute-Savoie a better place than Savoie?
Is French cheeses better than Swiss ones?
It works also well with Political local actions against global ones (especially when a mayor wants to keep his electors etc...)