Yes, these 'corn crib' style cages are common in American zoos. In fact, many U.S. zoos have junkyard porcupine exhibits for a variety of species. Take a look at some of these beauties:
@birdsandbats you must be having a laugh? The majority of these enclosures are absolutely disgraceful in terms of animal enrichment and core welfare. North America? They look like cages I’ve seen in 3rd World Countries!!
@TriUK I think birdsandbats was being genuine. The enclosure at the top does offer a lot of climbing room, especially when you compare it to some of those examples provided. Could it be better? Certainly - but for one animal I'd hesitate calling it "disgraceful".