Flying AA to the USA ex-DUB is infinitely cheaper, even with connection costs. In addition you get a better cabin, better food, cleaner aircraft and ... US pre-clearance at DUB, which is painless and saves hours of queues/lines. "The only way to the USA" ...
https://matrix.itasoftware.com 
PS| Matrix takes time to learn, but basically scrapes ALL airline websites for fares. the sub-set of google fares isn't as comprehensive..