The civil war era folk songs "The Irish Volunteer" and "We'll Fight For Uncle Sam" both state that the army (or at least the Irish portion of it) loved General George McClellan, even after he was removed from his command position.
My understanding was that McClellan was regarded as an inept battlefield commander and he had no particular ties to Ireland, being of Scottish descent.
I realize that basing my historical understanding on song lyrics is a recipe for misunderstandings, but it does seem like a good way to gauge the barometer of popular opinion at the time.
So with that in mind, my question is this: Did the Irish Americans love general George McClellan as is implied, and if so, for what reasons?
I answered a question about McClellan a couple of years ago that doesn't touch on the Irish phenomenon, but does expand on why McClellan was so popular with the Army of the Potomac. While not exactly the answer you're looking for, OP, I think it does get to the heart of why so many of his soldiers, Irish or otherwise, loved him so much.
Check it out: https://www.reddit.com/r/AskHistorians/comments/3e2vmb/why_were_george_mcclellans_men_so_loyal/