Sausage is banned because we american are so afraid of diseases*, that certain type meats that have been smoked, but not cooked are considered raw, and raw meat could carry diseases-- so its banned, customs to be honest, they will let you take most any thing out--except weird stuff--Cadilac Coupe de ville, ie, Its when you want to bring stuff in they object. So no problem leaving the US with flour-- just don't bring English flour here!
*as an aside, our being parinoid has some use, since USDA blocked british beef right at the start of BSE.
Coming from a irish family, i did get raised on smuggling stories, (how relations smuggled canadian fur coats into Ireland, sans tax and Irish whiskey into England, during WWII) and i smuggled (well i packed it in a suitcase, and forgot to declare it) a 10lb Ham into Japan!
Its not just US customs-- try driving into California with out of state plates.
Its a scene right out of grapes of wrath. the california authorities stop your car and inspect it-- to make sure your not bringing contraband!
