Americans eat both - the sugar/salt laden one all the way to slightly crunchy natural peanut butter. Most folks grew up with the processed stuff that doesn't separate when sitting on the shelf, though (not all natural).
But more to your question: Most folks spread it on fruit, some veggies, or on a sandwich, much thicker than butter or cream cheese. Too little peanut butter makes for a dry sandwich, especially if you aren't eating jelly along with it. Even when you are eating pure nut butter, it is easier to eat a lot of it. It is similar to someone drinking fruit juice or a smoothie (blended fruit only) can consume many calories in a sitting more easily than one would do with whole fruit. The body perceives it a bit differently with less chewing and whatnot.
But more to your question: Most folks spread it on fruit, some veggies, or on a sandwich, much thicker than butter or cream cheese. Too little peanut butter makes for a dry sandwich, especially if you aren't eating jelly along with it. Even when you are eating pure nut butter, it is easier to eat a lot of it. It is similar to someone drinking fruit juice or a smoothie (blended fruit only) can consume many calories in a sitting more easily than one would do with whole fruit. The body perceives it a bit differently with less chewing and whatnot.