Other than chocolate chips, and I really can't be a*sed breaking up a bar of chocolate and now had no access to a Costco (although I tried the chips out of there and found them tasteless), and Amy's and Morningstar, the things I miss are seasonal. Like Williams-Sonoma pumpkin and those crispy onions at Thanksgiving.
But on the whole, I can't remember a lot of foodstuffs and as I haven't been there in so long, it will be like looking at it with new eyes.
I do long for Newman's Own microwave popcorn and would love more regular access to salsa verde.
As I have little tolerance for lactose, though, I found a lot of American foods too creamy and cheesy to eat even when I was there.