it's like british biscuits. if they came here and asked for a biscuit for desert, they'd be sad at what they got.
They wouldn't ask for a biscuit for dessert (those are for teatime). But they would ask for a pudding. And then they'd be disappointed with what they got.
in england, pudding=generalized 'dessert' word, though there's a basis there for suet-based desserts or something. and what Americans know as pudding they call "delight" and is not too popular, they go for the step-up of mousse.
Step up of mousse? That's what we put on our hair! A pudding should look like this: