[dirtyroboto]

Beef jerky can be found here in many places. Very good quality jerky can even be found in Donkey.

Tacos, nachos are not so hard to find and tortillas are very easy to come across.

Best advice for anyone here and looking for this stuff is to go to your local indian resturant and ask where they buy their stuff.
This way you will find a really good shop to buy stuff you wont find in normal Japanese shops.

Caution on fine cheese as they will confiscate it if they find it. I have bought cheese in from the UK with no trouble though.

I don't think I have seen Fluff over here but I would guess its not a good taste for their pallet.

I would suggest bringing stuff from your home state or general USA like key chains, disney stuff, pens or the like.
As for food stuffs get locally produced honey or other preserve, also pickles go down well here.
Try to buy something that suggests a season - Spring/summer/autumn/winter as this will also go down well.