I am a bit confused, Shauna Skye. Is your British boyfriend alleging that peanut butter is unknown in Britain? That is very very very far from the truth! Perhaps he is grossed out at the way that (it seems to me) Americans place peanut butter on the "sweet" side of the sweet/savoury divide. To me as a Briton it is definitely a savoury item - it has salt in - to be spread on toast, classified alongside (say) Marmite and pâté. I must say that Reese's Peanut Butter Cups is a totally disgusting thing, but that's just my opinion. Do American shops sell sugary peanut butter?
Regarding sweet/savoury, during World War 2, many Brits were "grossed out" by seeing visiting American soldiers spreading jam on steaks, although we do have gammon steak with pineapple and also turkey with cranberry sauce I suppose.