Yeah the title sucks, I know. A spin off of the slurpee thread, but I know of only a few regional items that Americans can't get and a few that we can't get only available in the US.
Ketchup chips are a personal fave for me and I believe are only now making their way into the US, though they are crappy Lays IIRC. Old Dutch are far and away the best, making your fingers red with the dust on them. Yum.
Red Vines are not widely available in Canada and a must for me on each visit south. 7-1 lb bags last visit
I absolutely love those things.
Frankenberry is uber regional. Even just before Halloween last year in Cincinnati I couldn't find them, most tragic. Fortunately Scott has a quasi-nearby source to send me my fix a couple of times a year. We actually used to have these in Canada for a period of time, but no more. Forgot to get my bobblehead last batch
Beer is not quite junk food (it's more of a health food IMO) but is obviously quite regional. What else is out there?