For expats:
Tylenol and Advil- sounds funny I know but cannot get through the winter without them and no I am not addicted!
Cheerios original cereal- have found the honey flavored one but still have not seen the original Cheerios.
Office supplies
For both expats and Italian friends:
High count cotton bed sheets- I always buy new sheets in LA when I come home since I find the cotton to be nice, compact and you really don't even need to press them (great advantage). Remember that bed sizes are different in Italy and a Queen American size will fit a matrimoniale Italian size.
Designer Makeup- you can get some real bargains in the USA with the buy one free gift system. This just is not the case in Italy.
Athletic Shoes & Levi Jeans - These are very expensive in Italy.
Clothing - Casual wear like tshirts, jeans, and sweatsuits are much cheaper in the USA.
Electronics - these too are much cheaper in the USA
Baby clothes, toys, accessories- No, there is no Target out here so stock up on as much as you can!
Books and Music- I know you can get these off the net but they make good gifts to bring back. I like to buy English language books for my children too.
Housewares- kitchen towels, pot holders, table cloths, place setting table mats, runners, etc
Christmas decorations
I am sure there are a lot more but these come to mind. Let me know what your favorites are I may have left out.