Please give them back all of their rubbish TV shows. We don't want their kind over here!
Oh, and Baked Beans, Custard Creams, Twinings Teas, some really good chocolate such as Hotel Chocolate and the Benny Hill theme music to play while US customs are checking it all out?
They sell cadburys creme eggs and dairy milk and everything in America.
I would say the most bitter english marmalade you can find, pork pies, colmans mustard.
As for taking food, its much like bringing it into the UK. No fresh or unprocessed foods. Stuff like sweets and bread are fine, ham no.
EDIT: Actually ham may be touch and go.

About the chocolate thing, American chocolate is made differently I believe.