This doesn't prove your statement. All you're saying is that it was worse when they got to the USA. You can't deduce that they weren't leaving because of persecution.
Well, it is quite close to Ireland, and you know, people are dying and all that. I'm guessing it was significantly cheaper to move to Great Britain. In order to make a conclusion though, you'd have to see what these people did after they arrived in Great Britain. They may have stayed temporarily, and emigrated the main island shortly afterwards.
Such actions were not uncommon throughout all of medieval europe though.
But, in your own words, they hadn't been sovereign for "centuries" :]
Unfortunately, the perception of the people is what matters. If they feel they are being persecuted, then that is a viable reason for the emigration. If, upon hindsight, we look at it and say "You know, it wasn't really persecution" based on some application of the definition, it wouldn't mean that those that left because they felt they were being persecuted are wrong.
Having said that, I'm not sure how you can say that "it was Governmental stupidity and an unwillingness to disrupt the cash flow they were getting from Ireland's other food exports" while still holding the idea that they were not subjected to ill-treatment. Maintaining the food exports of Ireland while the people are starving in a famine is not ill-treatment?
And you could argue that you might be a bit bias in favour of it. It seems as though you live there based on your other posts, so it wouldn't surprise me at all if you're defensive about it. However, I believe Meta is also a Brit as well.