Well, firstly, in the UK we tend to call it ‘macaroni cheese’ rather than ‘mac and cheese’. Secondly, in America they tend to make their mac and cheese on the hob in a saucepan, whereas over here we pop it in the oven and bake it (for those irresistibly crispy bits on top). The cheeses are also slightly different - in the UK, Cheddar is the go-to (perhaps a bit of Red Leicester in some recipes), while in the US they use all sorts like mozzarella, cream cheese, Monterey Jack etc. You are also more likely to have it as a side dish in America (which is similar to how they serve it in the Caribbean), whereas in the UK it is seen as a main meal.