I swear I'm not picking on you but I see this line all the time when US-EU gas price comparisons are made and I just can't buy it from a logical POV. So I thought I'd get all anal and play with the stats :-)
The average US driver does about 13,500 miles per year: http://www.fhwa.dot.gov/ohim/onh00/bar8.htm
The number I keep finding again and again for UK driver is 9,628 miles a year (which sounds very low to me but I'll roll with it). That's almost a spot on 40% extra for the US driver (for a country with 42x the surface area, to be fair). OK, cool.
Given a US gallon of gas in the UK is about $8.25 compared to the current Californian average of $3.77 and the US driver is only driving 40% more miles on average, the US driver is still spending way less money on gas and would need to drive significantly further distances to make up the difference.