Why are jet fuel prices very similar in North America and Europe, yet automotive fuel prices are very different? Why is the pricing difference of jet fuel between North America and Europe extremely small, unlike automotive gasoline?

As of June 22, 2018, the prices in USD per barrel of it between the two continents are 88.0 and 87.8 and slightly older data confirm the existence of a small difference (I have not encountered a comprehensive dataset). Yet automotive gasoline in Europe usually costs 2-3 times the price it does in the US, comparing each US region to the very roughly analogous European one (based on income, geography, etc.). Why is this?
Jet fuel for international commercial aviation is effectively not taxed due to an agreement between ICAO member states. (See here ICAO PDF  ). Therefore the prices closely track to cost of production and distribution. These are similar worldwide. Differences exists due to local taxes on companies, difference in costs of transport, effects of competition on price etc, but these effects are limited. 

Automotive fuel is taxed. I am originally from the Netherlands, where we have one of the highest taxes in the world when it comes to fuel taxes. Petrol costs at the moment approximately 1.66 Euro/litre, of which 68.84% is taxes. 

In the US, the average total tax (federal plus local) is \$0.4818 on a gallon of gas (equivalent to \$0.1289 per litre).

So the difference in tax makes most of the difference in automotive fuel prices.

Sources: wikipedia