As for a change in the Anthem, Jerusalem was mentioned, the only problem I see with that is that it is named after a city that is not in the UK. Jerusalem is in Israel. That is like America using an Anthem named “Paris”. It seems odd to me.
‘Jerusalem’ the poem (set to music) isn’t literally about the actual city of Jerusalem, it’s about England.
In fact it’s specifically about Jerusalem not being in England 😄 It’s a warning about not being complacent and too nationalistic and it’s sung frequently by people who are complacently nationalistic.
"The poem was inspired by the apocryphal story that a young Jesus, accompanied by Joseph of Arimathea, a tin merchant, travelled to what is now England and visited Glastonbury during his unknown years.[2][3] The poem’s theme is linked to the Book of Revelation (3:12 and 21:2) describing a Second Coming, wherein Jesus establishes a New Jerusalem. The Christian church in general, and the English Church in particular, has long used Jerusalem as a metaphor for Heaven, a place of universal love and peace.[a]
In the most common interpretation of the poem, Blake implies that a visit by Jesus would briefly create heaven in England, in contrast to the “dark Satanic Mills” of the Industrial Revolution. Blake’s poem asks four questions rather than asserting the historical truth of Christ’s visit. Thus the poem merely implies that there may, or may not, have been a divine visit, when there was briefly heaven in England"
https://en.wikipedia.org/wiki/And_did_those_feet_in_ancient_time