63.7% of the retail price (42.7% tax, 21% sales tax)
Interesting. Taxes on gasoline in the US seems to be much lower than taxes in the Netherlands:
http://en.wikipedia.org/wiki/Fuel_taxes_in_the_United_States
Wikipedia said:
[...] for a total US average fuel tax of 49.3 cents per gallon for gas [...]
And with an average price per gallon of $3.38, taxes account for roughly 14.6% of the retail price in the US ($0.493 / $3.38), a paltry amount compared to the 63.7% portion of the retail price due to taxes in the Netherlands.
Now if we take the average price per gallon in the US and subtract the average tax amount ($3.38 - $0.493), we get about $2.89 per gallon before taxes. If this were only 36.3% of the retail price of gas, as in the Netherlands, and we solve for the total price ($2.89 / 0.363), we get a final price of about $7.96 after taxes.
So, it seems that taxes do indeed account for the entire difference between gas prices in the US and the Netherlands! This worked out better than I thought it would haha.
EDIT:
By the way, this would mean an effective tax rate of about 17.1% on gas in the US ($0.493 / $2.89), and an effective tax rate of about 175% in the Netherlands (($7.96 - $2.89) / $2.89). That makes the difference seem so much bigger, wow.