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A Roth IRA conversion involves transferring retirement funds from a traditional IRA or 401(k) into a Roth account. Since the former is tax-deferred while a Roth is tax-exempt, the deferred income taxes due must be paid on the converted funds at that time. Yes the US will tax you and no standard deduction will prevent that tax.
Ireland will not tax you on the conversion
No it is US tax law on IRA transfers
You are not required to report on Irish return
Here is the US law 26 CFR § 1.408A-4 - Converting amounts to Roth IRAs.
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