How lovely that you're researching your Irish roots. Sometimes we have a family member that just eludes us for a long time! Hopefully our list of resources
can help you tap some previously untried sources.
Do you know what port in America your ancestor arrived at? Sometimes the lists of those entering the country can hold clues, and that's especially true if you keep in mind that spelling wasn't always as it should be when passengers were registered.
Also, his obituary may have been based on his or family members' recollections, which means they may be off by quite a few years, so expanding your search to 5 or even 10 years either way may help you find more. Do you know if he travelled to the US alone or with one or more family members?
Wishing you succesful searches,