Nationalism and religion have a lot in common. Yet nationalists and religious people will quickly deny this. But both nationalism and religion are about tribal rituals, members and not members, ours vs theirs, inclusion vs exclusion. A gene pool vs a non gene pool. I know this. I am Jewish but I am not religious, still I am a “member of the tribe”.
Religion and God most likely have nothing in common. This is because most likely God does not exist and should something like God exist it is extremely unlikely that somehow this God would belong to a single religion and not other. Religion, which is a form of nationalism, which is a form of tribalism.
Here’s an article that I wrote about what happens when a country gives up religion as Spain mostly did.