In answer to the original question, I don't know why there would be Irish gunmoney finds in the US. There is no reason for it to be there. They were intended as emergency issues to pay for goods and services in Ireland that would be redeemable in silver once James II retook the throne (which of course, he never did). They probably weren't trusted much by those Irish who weren't fanatically optimistic Jacobites due to their low intrinsic value, so I can't see any reason why they would have been exported to use as currency outside of Ireland...
