Hush Puppies are shoes, dear. 
racer72, as you might have noticed, Pier 39 is a great big honkin’ tourist trap. San Francisco’s food is world-famous, but not because of Pier 39. I promise you there are plenty of restaurants in the Bay Area that know what good salmon is. Try Chez Panisse next time.
I’ve experienced this both ways – when I lived in Europe, there were American foods I couldn’t find and when I moved back there were European foods hard to come by. Kohlrabi was one of my favorite root vegetables, but it’s damn near impossible to find it here in Chicago unless you’re in Eastern European or Asian markets. Also, fresh goose liver was available in every grocery store in Budapest (top quality and affordable, too–something like $10-15/lb), but here it’s only found in specialty shops and when you do find it, it’s far too expensive to enjoy.
However, when I lived there, it was awfully hard to find decent peanut butter (but peanut butter itself did exist), steaks were butchered in funny ways (I just gave up on Hungarian beef, except for stews), my favorite Mexican ingredients were non-existant (tomatillos, chipotles, masa harina), seafood was abysmal (landlocked country and all.)
Two thing I 've heard lamented by people who’ve moved away…
One friends moved to Brooklyn recently. I almost never talk to her, but every time I do, she mentions the lack of burritos. Each of us grew p walking distance from a Gordo’s, and I couldn’t live any other way.
And there was a thread her maybe a year ago where people expressed surprise that “way out there” you can buy pizza by the slice! My chin still has rug burn from when my jaw dropped.
I only got to go there once, and I grew up in that little town. IIRC, you went in and got seated, ordered what drink you wanted from the bar, and picked an entree off the very simple menu. I picked Roast Beef. Then food started to arrive. First, salad, with yummy dressing. Then soup and bread. Not small bowls, either, and as much as you wanted. Then beans. Then spaghetti. Then French Fries. And pickled tongue. And probably other stuff I don’t remember. And my Roast Beef was two slices about 1 1/2 inches thick. There were vegetables with that. And then they asked if we wanted dessert. No thanks, just roll me home!
Good Italian food. It’s all over in the Philadelphia area. Not so much in New Mexico - the Olive Garden is not Italian, and Pizza Hut is not real piza.
Similarly, you can’t go a mile in Santa Fe without stumbling over at least one authentic Mexican/Southwestern restaurant. In the Northeast…Taco Bell, as stated, is not Mexican.
Southern table wine, AKA sweeten iced tea.
Not exactly a food, but a staple none-the-less.
Hands down - produce. I spent more than half my life in the Puget Sound area, and grew up in an area which still had abandoned homesteads in the neighborhood. As kids we raided these old orchards and brought fruit home by the grocery bag. Then there were berries, cultivated as well as wild. I so miss blackberries, thimbleberries, huckelberries, etc. What wasn’t available by the wayside, we could grow. Gramma had a gigantic garden, and my brothers and I were encouraged to eat our fill as soon as we were old enough to pick for ourselves. If I went into detail I would have to write a book length post, but Life was good.
Here, all produce is barged up, very slowly. Stuff freezes, and a lot of produce does not respond well to freezing, think lettuce. Tomatoes have pale color, no flavor and are dry, blech.
I was ten years on the island before I made a visit home. We got to my (other ) grandparent’s home, and my grandma presented me with a bowl of Red Delicious apples. I was transported with joy, they were huge and fragrant, and so, well, delicious!
Blackberries: Kudzu of the North.
Like Zoe, I grew a taste for avacadoes after guacamole. Guac’s got smooshed avacadoes, diced onions and tomatoes and lime juice. Options are chopped cilantro and jalapenos. Add salt to taste. Serve with freshly fried tortilla chips or, blasphemous as it may be, Tostitos Lime Flavored chips. Yum!
I take all sorts of ethnic choices for granted. We make dinner decisions here by cuisine, not restaurant - so the question “What do you want for dinner?” is best answered “Indian,” “Thai”, “Brazillian,” etc. Going just an hour south to my mother’s, the most ethnic choice is Chi-Chi’s.
For specific foods, it would have to be lots in the produce section. Kolhorabi, as one poster mentioned, burdock root (gobo), fancy lettuces, cactii, mangoes, papaya, jicama… When I’m in some other places, it seems like there’s corn, carrots, peas or green beans and that’s it.
She’s got the right idea. I’ve tried black eyed peas and they are a really inferior food.
The only thing I can think of that I miss when I’m not in Michigan is pasties. Although they are typically a UP thing, there is an excellent pasty shop near my parents’ house.
The thing most people miss about living in Michigan is White Castle burgers which I can’t stand.
Oh, and sweet tea is catching on up here. I have to make sure that when I order my iced tea at our local steak house that they don’t serve me the sweet tea (I’m diabetic)