I think you are splitting hairs here Ebbie, in an effort to prove there is no US custom.

When I say American in the context of Irish immigration, I'm always thinking both Canadian and US immigration because the two countries both had sizable Irish immigration groups coming in the wake of the Irish famine and it's Devotional Revolution aftermath.

I don't think this particular custom is regional. I think it is universal throughout Canada and the US. I've cited two examples, from both countries.

I have no way of proving this, of course, because folk customs associated with anti-ethnic and anti-religious bigotry tend to be covered up, glossed over, denied, etc.