Irish accents and North American accents share some similarities, but they are also distinct from each other. Both accents tend to have a more pronounced "r" sound, and some vowel sounds are also similar. However, Irish accents typically have more variations in intonation, rhythm, and pronunciation than North American accents. On the other hand, Received Pronunciation (RP), which is the standard accent of British English, is generally more similar to other British accents than to North American or Irish accents. RP has its own unique features, such as a lack of regional accents and a focus on clear, precise pronunciation. In summary, while there may be some similarities between Irish accents and North American accents, they are still distinct from each other. RP, on the other hand, is generally more similar to other British accents than to either Irish or North American accents.

I don't know if it's closer, but there are certain things that may be, i.e. they both tend to pronounce Rs, whereas RP doesn't really. I believe this is called RHOTICITY.

As an American, I don't think the Irish accent sounds North American at all, so I would say it's closer to the English RP. Britons might say the opposite, though!