A church building, is a building used for Christian worship services and other Christian religious activities, whereby the word "Christian" is most important.
However Potala Palace (
https://skyscraperpage.com/cities/?buildingID=5297 ) and Mole Antonelliana (
https://skyscraperpage.com/cities/?buildingID=19834 ) are and were never used for Christian purposes and are therefore no churches.
In my opinion one should put these objects in a new category "religious building (non-Christian and non-Muslimic)", when one wants to keep the category "mosque". An other idea would be "religious building" for all religious buildings with subcategories "church", "mosque" and "other".