Pre-tax income of $120k would net about $95k in the US for a married man with 2 kids and a house in a tax-free state (Texas, Florida, etc.) 8% growth isn't a stretch, it's the average return for S&P 500 over the past 100 years.
For a single person without a house and without dependents, the after-tax income is actually about $76k in CA and $87k in TX, according to ADP's online calculator.
A 50% aggregate tax burden is a choice a small fraction of Americans make. As others have pointed out, most Americans have far lower aggregate tax burdens.
Also 8% growth a year is quite a stretch given that risk free rate is 2.64% (10-year treasury yield), and inflation eats 2% a year...