You can't import haggis because one of the ingredients that is usually used to make it is Offal, which comes from cows. English cows had the whole mad cow thing. While the Scottish cows were largely unaffected, all beef imports from the UK were banished in the US.
New York City has banned any food with trans-fat in it. Missouri (or was it Mississippi?) wants to ban serving certain foods to fat people. It's the nanny-state in action. It's one thing for the government to tell me that I shouldn't hit nocal in the face with a shovel, but if I want to hit myself in the face with a shovel why should I be stopped?