Indeed very country dependent. Netherlands is 50% (used to be 52) starting around € 55k. That sounds higher than Germany, but then in our case social security and an allowance for elderly is included. So in the end I guess the part of your income you pay is similar in most European countries it's just structured differently. And indeed, it's a very big part.
The US has a low income tax, but then the middle class needs to pay for their own health insurance (at $ 600 a month), disability insurance and pension etc. which means they end up not far different from Europe.
The big difference is at the extremes of the scale, the very poor and the very rich. In the US the poor don't have any health insurance, disability insurance, or pension etc because they cannot afford it. And the very rich in the US are way better off than they would be in Europe, because for them a low income tax greatly outweighs the costs of insurance etc.