You are mistaken. Currently, the higher income you have here, the higher tax rate you have, where the highest tax rate on income sits at 47%, which you get hit by when your income is above 300K/year. People between 60K and 300K sits at 45%.
And then there are regional differences, someone in Andalucía don't pay the same amount of taxes as someone who lives in Catalunya for example, where the top tax rate is 50%.
Even taking into account other taxes we have, you still end up paying more in taxes the more you earn, unless you start engaging in schemes to lessen your tax burden, obviously. Although the social security is capped, so it does increase slower once you go beyond the cap, but it doesn't start regressing which your comment hinted at.
Edit: important to note that the tax rates are all marginal tax rates, maybe that was a bit unclear.
This is basically inviting your best and brightest to move to the US and other low tax countries.
Assuming your money comes via income and you are not doing anything exceptional to optimize taxes, you are around that 50% or so rate on incremental income nearly anywhere you’d be able to make such incomes in the western world. Normalize for things like health insurance and it’s really not worth even considering a move for tax purposes in most cases.
The US is known as low taxes, low services - but it’s really within about 5% for high earning professional workers compared to even most social democracies. It’s a decidedly high tax low services place to live.
The largest difference in taxes in the US vs rest of the developed world seems to be the high tax brackets start much earlier on the income scale. It’s much better (for taxes at least) to be in the US as a median wage earner and it’s usually not remotely close.
Where things decouple is how capital and other forms of investment income are treated. That gets too complicated for me to understand, but it’s clear to me that a charitable take would be tax code has not kept up with how the wealthy increasingly earn their income.