As a devout Atheist I have difficulty with the present anthem and any other religious songs. I sing the present anthem, but with little enthusiasm and no belief in the words whatsoever.
Replacing it with Jerusalem seems a crass retrograde step for a multi beliefs country like England. Now if we sang the first couple of verses of this...
Come, cheer up, my lads, 'tis to glory we steer,
To add something more to this wonderful year;
To honour we call you, as freemen not slaves,
For who are so free as the sons of the waves?
Chorus:
Heart of Oak are our ships,
Jolly Tars are our men,
We always are ready: Steady, boys, Steady!
We'll fight and we'll conquer again and again.
We ne'er see our foes but we wish them to stay,
They never see us but they wish us away;
If they run, why we follow, and run them ashore,
For if they won't fight us, what can we do more?
Chorus:
Heart of Oak are our ships,
Jolly Tars are our men,
We always are ready: Steady, boys, Steady!
We'll fight and we'll conquer again and again.
I'd go for this as its not exclusive to our fellow UK nations, but has a rousing tune and no reference, in these verses, of imaginary friends.