True in part. There were Irish immigrants to the South that fought for the Confederacy. There were Irish that immigrated to Europe and fought with Napoleon. There were Irish that fought with the English against the French. There were Irish that immigrated to Canada and didn't fight anyone. There were Irish that didn't emigrate at all. But the majority of Irish immigrants to the USA in that period were to Northern cities. There were many that fought for the Union. Hence the qualifier.
As for calling the comparison a straw man. You are just unhappy it is accurate. The America-haters handbook? Is that where you find your justifications to remember with fondness a slave regime? How many would you own?
< yawn >
Tell me about the draft riots in N.Y. again...
When you can support your fatuous analogies, ping me, until then it's your story, tell it how you want.