So now check this out, 2019 data:
USA
avg engine power: 192 kW
avg kerb weight: 1768 kg
avg fuel consumption: 8.6 lge/100km
gasoline price: 0.79 $ PPP/litre
https://www.iea.org/articles/fuel-economy-in-the-united-states
UK
avg engine power: 110 kW
avg kerb weight: 1518 kg
avg fuel consumption: 6.3 lge/100km
gasoline price: 1.59 $ PPP/litre
https://www.iea.org/articles/fuel-economy-in-the-united-kingdom
German numbers are very similar to UK's.
The cheaper the energy the more wasteful people are with it, it's that simple.