the vast increase in distances the American needs to travel,

That should motivate to drive more gas efficient cars not less.

the average American car isn’t less efficient

It is less efficient in that they use more gas, weight and aerodynamics are part of that equation. many American cars have piss poor aerodynamics, and they are heavier for the same size of car, in part because of bigger motors and a cheaper frame based construction. The engines are also typically way less efficient, using big V8 engines with poor efficiency, that you would simply never see in Europe. The widespread use of giant cars like the Ford F-150 is insane. It’s almost like people in Nebraska buy them because they “need” to be able to carry a surf board to the beach 2000 km away. So yes American cars are way less efficient on average.

Maybe I’m biased because I’m in California

IDK maybe you are, California is AFAIK leading USA regarding emissions, when California set a standard, the auto makers follow it, and by proxy the rest of USA get cars that follow the Californian standard.
Problem has been for decades that where efficient 4 cylinder engines have been standard in Europe, USA has used wildly inefficient V8 engines. So no the Americans have not been using the same technologies nearly as much. For instance when we got 4 valves per cylinder in Europe, Ford was way behind, and advertised what they called lean burn. A way inferior technology, that both yielded fewer HP for the same size engine, and had lower gas efficiency.

In Europe developments have been very much on the weight too, like the VW Polo 3l that could drive 100 km on 3 liter of gas, or 62,18 miles 0,79 gallon or 78 miles per gallon.
Part of achieving that was to use magnesium for the rims, and an extremely efficient 3 cylinder engine. This car was very popular here in Denmark, despite it was very expensive for the driving experience. But here most people are actively engaged in lowering the environmental footprint, while even in California such a car is probably unsalable.

As an example we don’t currently feel the oil crisis at all, because our household has zero dependency on oil, we use wood pellets for heating (Denmark is a relatively cold country), we have solar panels that cover 80% of our electricity needs throughout the year, and we drive an electric car we can charge from the panels.
Denmark as a country has 82% as a whole, so what we buy from the grid has similar efficiency, reducing our dependency on non renewable energy to only 4% for our household.

80+% of new cars sold in Denmark are electric.

I know Denmark is among the leaders in EV in Europe, just like California is for USA. But I expect you can see the difference between a European leading nation and a leading state in USA.

I know many Americans try to be more green, but the disinformation allowed in marketing makes it harder, and the lack of actually green production makes it near impossible.
In Europe we have way better democracies, and many European countries have parties to represent them that have a green agenda. An American voter mostly doesn’t even have the option to vote green.

Sorry for the rant, but as you maybe can see, USA is mostly dysfunctional in this area, and failed to learn the lesson of the oil crisis in the 70’s, while most of the rest of the world did. Which is extremely unfortunate, since USA has all the natural conditions that exist around the world to develop and implement renewable energies, and USA had the biggest research and development capacity for many decades. So USA idling along on a free pass has been very damaging to the global development too.