I spent a few years in Texas and often travel by road cross country. I do have to say, finding a dollar store chain of local is a blessing in the big empty in-between.
Good point, reliability is key. Selection is narrow, limited by space, but they have a little of everything.
Healthy food is easy to find at these stores. I can put together a perfectly good home cooked meal from Dollar General no problem. Baking goods, dry goods, dairy, produce... again the selection is smaller than a larger grocer, but it's all there.
Dollar General has a much larger selection than an Asian 7-Eleven. It has "real groceries" (albeit a small selection) and many non-food goods like detergent, toys, shampoo, even cell phones and a small variety of clothing. It's kind of like they got a list of the top 10% best-selling items at Wal-Mart and made a store out of it.
Dollar Tree (and Family Dollar IIRC) are a bit different because unlike Dollar General each item is actually a dollar. They're a bit more akin to Daiso, if you visited any of those in Thailand, though again with a bit more food (though less than Dollar General, and in smaller packages).
> Dollar General has a much larger selection than an Asian 7-Eleven.
That is surely because a 7-11 in say Japan, Korea, or China are part of vertical, dense infrastructure. You don't have miles of space in between things.
And I would be curious if Dollar General has that much more of a selection compared to some of the big 7-11 I've visited in Seoul.
Maybe I haven't visited the right ones, but none of the 7-Eleven (or FamilyMart, Lawson, OKmart, or CU) stores I visited in South Korea, Taiwan, or Japan had selections that close to those of the Dollar General stores I've patronized. In my subjective judgement, the difference is pretty big. This is not a knock on them, of course, just difference in business model, and as you say, regional/market context.