OP is confusing overall use which includes agricultural and industrial use with municipal use.

It doesn't really matter, ebcause it applies same to all countries, so it doesn't explain why Americans need to consume 4 times more water per capita (3794 litres) than Germans (855), while Czechs for instance even half of the Germans (422).

And don't go at me with average temperatures nonsense, Spain and Greece are warmer than most of the US and have half of US water consumption, Thailand little bit over half, Malaysia less than 1/3 of US consumption.