There was a documentary on last week about this, 'twas very interesting. Talked about how the romantics, following the French revolution, starting questioning what national identity was, which gave rise to a lot of nationalistic ideas and poetry (including popular tunes such as Jerusalem)
I didn't see the programme but I've always thought that William Blake's 'Jerusalem' wasn't about Nationalism but how Jesus could exist everywhere and anywhere, even in England. Myth has it that Jesus did visit England (and did those feet, in ancient times etc) because his uncle Joe (Joseph of Aramathea) was a tin merchant who sold tin to the Romans, naturally most of that tin would have come from Cornwall, it would have been churlish for uncle Joe to visit Cornwall and not take his nephew along for the ride at least once, maybe do some surfing, and that's how that myth came about.
Whenever I visit St Mawes on the Roseland Peninsular, I always make a point of stopping at a little church in St Just in Roseland, the church is on the edge of a lagoon, likely an ancient port, which is on a creek off the river Fal, I used to moor a boat there, nice spot.
The churchyard is a stunning walk with gravestones depicting old sea captains and the like. Sir John Betjeman called it the most beautiful churchyard in the country, and having noted Slough as a bit of a s**thole, he knew his stuff. Anyway, if you wander into the church, reflect a bit, maybe light a candle if you're feeling extravagant, on the way out, pick up the free leaflet on the church history. It does indeed categorically state that Joseph of Aramathea
might have visited the 'port' to buy tin and
would possibly on one visit have brought his nephew Jesus along for the ride.
Anyway, notwithstanding all that, if you ever wander through this churchyard to the edge of the creek, look out across the Fal toward the sea and hear the church bells ring, you might just start to understand how beautiful a country England is, and how there really is nowhere in the world quite like it.