Who cares about marginal tax rates -- that is the rate you pay on your last one Euro of income. What really matters is effective (blended) rate.

In the US, there are normally two levels of income tax (Federal and State), and, rarely, there is also a local/city income tax (like New York City). Sorry, I am not familiar with the Irish income tax system. Since you mentioned that you are in the 24% bucket, your gross income is more than 100K USD. (Congrats: That is pretty high in Ireland where the median income is about 38K EUR.) If you add up all income taxes in the US (Federal + State + Payroll), I guess it is pretty close to your 35% effective rate in Ireland. So really, not so different.