First of all, yes, labor is taxed much higher in Germany than in the US (PPP adjustment already takes VAT on prices into account, so that doesn't matter in this case). In fact, Germany has one of the highest taxations of labor in the world.

What makes this analysis tricky is disposable vs. discretionary income. The US clearly comes out on top when it comes to disposable income (labour is taxed too much in Germany compared to capital income and wealth).

The picture gets more complicated when you look at discretionary income, which also accounts for regular bills, such as rent, college tuition, out of pocket expenses for health care, childcare, and such. All the taxes you pay in Germany do also pay for something, after all. There is unfortunately very little data for this type of comparison.

You would also need to adjust for the huge medical expenses Americans face if you are doing that as Germans don't have that. Maybe the 401K savings Americans do for retirement (if Germans have a better societal retirement payout than Americans). And the other social benefits that are accounted for by German taxes that Americans still have to account for in some way. You can't just lump those in on the Germans and not account that Americans pay it some way as well.