Comparing a Dutch payslip with another country's
A Dutch payslip usually carries one deduction, the loonheffing, which combines wage tax with the contributions for the state pension, survivors' benefits and long-term care. The premiums for unemployment and disability insurance and the income-related health insurance contribution are paid by the employer on top of gross, so a Dutch net figure is not reduced by them while the employer's cost of the job is.
Two things sit outside the Dutch payslip and matter in any comparison. Every resident buys basic health insurance from a private insurer and pays that premium out of net pay. And most employees pay into a sector or company pension fund, whose contribution depends on the fund and is not shown here. Against an American state the first point narrows the usual gap, because neither net figure has paid for health cover yet; against another European country it widens it, because most of them fund health care from contributions already on the payslip.
Equal purchasing power, not the exchange rate
The second gross salary on this page is the one that buys the same basket in the other place, derived from official purchasing power parities. Both sides then go through their own payroll rules, and what is left is brought back to one set of prices in the row labelled real take-home. Because both columns begin with the same real income, the difference at the end is the tax and contribution systems and nothing else.
Where the other side is a US state, its price level is chained rather than measured: Eurostat publishes a parity for the United States as a whole, the Bureau of Economic Analysis publishes an index placing each state against the American average, and the state figure is the first scaled by the second. The page notes this above the tables. Against another euro country the exchange rate is one to one, so the whole difference in the second salary is prices.