"I don’t know whether or not the song’s popularity indicates a feeling of understanding (and sympathy?) between working class people from Ireland and England,"
Apart from Walter's singing, I have no experience of this song - much of what has emerged here makes sense and I'm grateful for the information
It's not the type of song that I would have regarded as outstanding (over sentimental and music-hallish), but what immediately struck me was the similarity of sentiment between it and the Napoleonic songs, in that it suggested a sympathy for a cause espoused by two people, while being divided by politics, were united by their individual problems
The newly emigrated Irish were regarded as 'the enemy' because they were used by the employers to drive down the wages of the indigenous workers; the effects were dramatised superbly in Elizabeth Gaskell's 'North and South'
At the same time, there was a Europe-wide movement to improve the lot of the working man
This is not unlike what happened at the beginning of the 19th century when the French Revolution created similar parallels - Melville's story, 'Billy Budd' was one of the outcomes

The Irish Famine produced very few songs; as Nicholas Carolan once
said in a lecture on the subject, "People were too busy dying to sing and make songs"
The aftermath and the ongoing consequences of an at-least badly handled natural disaster produced many hundreds of songs throughout the rest of the century
I may be over-complicating a simple song, but I think this could well be one of them
Jim