I love Ireland, and went there twice. One of those times I took two days of a 9 day trip to research. The only family I was able to trace "across the pond" is my Rowley line to County Longford (center of the country). Records for the family appear to stop with the father who didn't come over, Hugh Rowley.
My Duffy line stops in Pennsylvania, Charles born about 1800 in Ireland. Charles went to Summit County, Ohio and was the first to attempt citizenship there (first on the list!). Those citizenship records appear to have been lost, so any gleanings as to his origin are also lost. I haven't given up, I'm just on pause for now. I've annoyed the local library, county records office, Ohio Historical Society, Summit OGS, and loads of others there for a while.
I wish you all luck!