What are some things which you cannot find in the States you would bring with you if you were travelling between the two countries?
Żubrówka in the United States
Because bison grass contains the toxic compound coumarin, which is prohibited as a food additive by the Food and Drug Administration, importing of Żubrówka into the United States was banned in 1978 by the Bureau of Alcohol, Tobacco and Firearms.
Poisonous, illegal and tasty, what's not to like? :)