Many communities have no grocery stores nearby. Those that are there are often understaffed. Meanwhile, dollar stores and McDonald’s are everywhere. Amerikkkan car culture and Suburbia has concentrated stores often like half an hour outside the city. If you don’t have a car it’s not accessible. Few want to carry a bunch of bags of groceries on a bus for an hour (if they have the transportation infrastructure). Healthy grocery stores like Whole Foods don’t want to go into poor communities because they can get more money from those who can afford the higher prices they want to charge. As these problems disproportionately affect non-white people, some have opted to call it “food apartheid” rather than desert as the latter suggests it’s natural.
I’m no expert, but as a USian who’s heard a bit about it I thought I’d comment. I can’t think of any further reading.