I don't believe there's any country in the first world where your take home matches the employer's out of pocket - in the US you've got healthcare, retirement matching, payroll taxes, other employment fees and a few other employer-side taxes. Most other countries follow a similar logic, relying on offloading some of the income tax burden onto the employer to prevent a total loss of tax income from judgement proof folks - it's always why withholding and tax refunds are so encouraged. If you've got proper or overaggressive withholding setup with your employer than it isn't possible for you to find yourself with a 10k bill in April that you can't pay - instead the government will return any wrongfully withheld income and you get a "bonus check".

In terms of the proportion 31% is relatively small honestly - employee charges in the US generally range somewhere in 40-60% but senior developers with families often have payroll overhead that can run upwards of 80k and can represent a much higher proportion of the employer's out of pocket employment expenses. These costs can be extreme at relatively hip progressive companies that employ some unskilled folks. Your 5k/month healthplan might be proportionally little on your 150k salary but if someone working in the mail room and earning 20k annual has the same benefits it'll work out to 300% their take home cost - this is why employers often segregate benefit packages to different pay ranges.