There is an interesting article in The American Conservative entitled The Once & Future Christendom by James Pinkerton.
I have hope for Europe. However, if it falls, that is not the end of Christendom. North Africa was Christian. It fell. Egypt was Christian. If fell. Asia Minor (the region enveloping the area containing most of the churches addressed by St Paul's epistles) also fell.
Christendom is, in a sense, the inhabited home of Christians.
Sometimes you you sell your house and move to a new neighborhood. However, the gates of Hell cannot burn down the house inhabited by the Christians.