We're in a culturally Christian country. (Most of us; I am assuming most posters are British.) Half our public holidays are based on Christian festivals.
Our art galleries are filled with art that has Christian themes (especially if they can get naked women into it, like Salomé, or Susannah - which I think is an Apocryphal story, rather than Biblical, but basically Christian; it means we are also culturally patriarchal.)
There's tons of literature with Christian themes, since before Chaucer. Even things like Larkin's the Whitsun weddings - that's a Christian festival in origin, even if it became the time when factories shut down for a break.
Villages, towns and cities will have originally had a church it cathedral at the centre, so it affects our architecture and so on. I'd expect pretty much every town to have at least one road named after a saint, usually the one from the local church.
Music, certainly classical music, includes a lot of Christianity - all those requiem masses and so on.
It's difficult to go out round much of Britain and not see something linking us to our Christian heritage, in a way we don't have with other religions, except in areas of larger cities. And mostly, because it's just there, and always has been, we don't really think about it.
Like Britain, most of Europe is culturally Christian in the same way. (Less so with countries which were behind the Iron Curtain, going by their public holidays, but even decades of communism didn't remove all traces, even if they tried.)