Automotive fuel prices are also very similar between the US and Europe, when comparing pre-tax figures. For instance:
The current pump price for regular gas in Pennsylvania is \$3.00/gal, of which \$0.77/gal is tax (\$0.184 federal + \$0.582 state), making a pre-tax price of \$2.23/gal.
The current pump price in Germany is €1.47/L. Before 19% VAT that's €1.23/L, and less €0.65/L fuel tax, the pre-tax price is €0.58/L, which at the current rate of exchange is $2.55/gal, about 14% higher.
The difference is simply that the total effective tax rate on gasoline in PA is about 35%, while in Germany gasoline/petrol is taxed at an effective rate of 153%.
For jet fuel sold to airlines, on the other hand, both places offer much more favorable tax rules, so as not to cripple the aviation industry. The total tax applicable in PA is $0.03/gal, and my understanding is that in Germany, both fuel tax and VAT are entirely refundable for airlines, so the net tax is zero. Since the taxation is minimal in both cases, the drastic difference in taxation doesn't exist, and so the drastic difference in retail prices also goes away.
Aviation gasoline tends to be treated more like other gasoline, and private pilots generally don't qualify for tax exemptions (and the price of avgas is rather high to begin with), so the differences there may be much more drastic from place to place than with jet fuel.