I eat peanut butter sandwiches and while peanut butter may be imported (as too much of our food is, and I'm not rushing into the kitchen to check its origin) it's not something you have to seek out as it's as readily available in supermarkets as any other sandwich filling.
As a child I remember that a lot of kids used to eat jam (what you call 'jelly') sandwiches, mainly strawberry. I never heard of anyone eating peanut butter and jelly/jam together until I was practically out of school, and I have no idea whether kids have taken it up over here, not being a parent. Personally I never understood the appeal of jam sandwiches, and I'm even more sceptical about mixing jam with peanut butter. I did use to eat golden syrup sandwiches, though...
