6) The 60% match rate is everyone, Canadians and Americans. I didn't include Irish because the Irish application rate to the US is very low, especially right after final year. I think there was one person in the last 4 years (they matched).
Typically Americans do better applying to the US because they do not require a work visa. This means less work for programs and no chance of you having potential visa difficulties that could prevent you starting on time. I don't know the actual breakdown between Canadian vs American applying to the US, though.
7) If I had to do it all again, I probably would, especially because I matched. If I didn't match than I would have 100% regretted it (...obviously, I suppose).
The main reason that I don't regret it is that being a doctor is the only thing I've ever wanted to do. If you can see yourself something something else, do that. You have to REALLY want it, because there's going to be a lot of stress and a lot of hard work along the way.
8) There is stigma about being an Irish medial graduate. Mostly a few comments here and there about how you couldn't get in to medical school at home.
But, in Canada anyway (sorry I can't speak about USA), there's no stigma career-wise. I've met Irish medical grads that became Chief residents, and that got great fellowships in many different specialties. Once you're in, it's all about how you perform as a resident. Nobody except for very elitist people cares about where you went to medical school 5, 10, 20 years down the line.
And there is WAY less stigma than being a Caribbean grad. The Irish medical schools are excellent, and I actually feel like I received a better clinical education at UCD than I would have in Canada. And it is well known, especially among residency selection committees, that Irish medical schools are more difficult to get in to.