…are non-US peanut butters less viscous?
Non-US peanut butters typically have only one ingredient (peanuts) and therefore you get peanut oil separating out that needs to be stirred in. American peanut butter (at least the ‘popular’ brands) tend to be so full of preservatives and shit that they hold their state.

it’s not the preservatives, it’s the hydrogenated oils that are added - basically they substitute some of the peanut oil that would separate out for oils that won’t separate (and stay hard, like a butter or like margarine)

even the “healthy” no-stir peanut butters do this