But how much of that is irrigated? As I understand it in California there is a lot of irrigated lawns. But I doubt the majority of lawns in the US is irrigated or watered.
Those in New Zealand can avoid watering, particularly if the lawn is kikuyu. It is a complete pain to maintain though as it grows very fast when it’s warm, wet and sunny. It makes you itchy is you lie on it too.
It depends on what species the lawn is. If it's the same species that grows naturally in vacant lots and by the roadside, it doesn't need watering unless there's a significant drought.
A lot of people (at least in the PNW) just let their lawn go dormant in the summer rather than water it. Since we'd be using city water in most places, it is expensive to dump that on grass.