Truck voltage I can answer to.  Air pressure I will leave for others.

European truck voltage is normally 24 volts, compared to 12V in the USA.

It is for a simple reason.  The higher the voltage, the lower the current, and the lower the current, the less cross sectional area is needed in the conductors (wires), so, the lighter the truck.  It may not amount to but a few kilos or lbs, but it all counts.

With the historically higher prices of diesel in Europe, as compared to lower prices in the USA, when you take the weight of all the wire that all the european trucks are not carrying around, compared to their USA counterparts, it represents quite a savings in payload.

You don't typically see tandem drive axles on tractors with power dividers in Europe either, for the same reason, they can't afford the weight penalty.

Same for the big horses.  The typical european truck does not have the 5-6600 HP engines, but make do with 3-400 HP engines.

Lots of other differences, all of which relate to saving weight, to reduce the cost of fuel.  A few years ago, when I became aware of this topic while talking to a British trucker at the Czech/German border, an individual who had lived and trucked in the USA, as well, and knew both systems, he was getting 11MPG, while the typical USA truck of the day was getting 6MPG.  At $3.00/gallon, that is real money.

rmw

Thank you rmw! Very helpful reply!

Sanjiv