My income is at the 24% level above, and I'm paying 52% marginal taxes in Ireland (or 35% of my total income after tax credits etc)
Their taxes probably are lower than yours, but probably not by as much as you think, and certain things like medical insurance are really expensive in the US.
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.
The 10% bracket is all under poverty level (the reasons this exists is somewhere between occasional part time work for seniors or teenagers, the standard deduction)
The 12% bracket includes ~50% of individual filers that are under most welfare levels. Does that 20% increase in tax rate make sense for that group? The Married/household rate covers the majority of American households, including median household income.
The 22% bracket... let's start with this is a 47% graduation increase versus the previous 20% increase (more than double)
The 24% bracket... again, a seemingly random increase of < 10% rate graduation increase
The 32% bracket... an 8 point rate increase, that's 25%...
The 35% bracket, back to a 3 point, 10% increase
the 37% bracket, even more decreasing, a 2 point, 6% increase
So; the rates of graduation increase are 10%, 47%, 10% , 25%, 10%, 6%; from a distance we can see that the 47% and 25% changes are definitely outliers; If, the top rates of change were at least at the top marginal incomes, it would make more sense.
It looks even worse if you also include the regressive 6.2% OASDI payroll tax. 16%, 18%, 28%, 30%, 38%, and 41% -- 25%, 55%, 11%, 26%, 8% (ignoring the employer's OASDI / Social Security)
Nc Income tax rates 4.5%
SC Income Tax Rates $0-$3200, 3% > $3200, 6.5%
Al Income tax rates $0-$500 2% $500-$2500 4% > $2500 5%