Correct, if the price in the US is $3 a gallon and the price in Europe is $8-9 a gallon then there must be around 5-6 of additional taxes in Europe.

What's your average distance driven per year? In the US it's 13,476 miles (21k km).

So because you drive longer, which of course produce more Co2, you should have a lower price? l/100km or mpg is not really the most important, what count is l or g per year. Last time gas prices where high sales of SUVs and trucks in US did go down, as soon as the gas price did go down sales of cars with terrible mpg ratio did go up

In Finland, the price is currently about $6 per gallon. Average car drives about 10500 miles per year & there's about 0.49 cars per person.