I've seen the occasional Westphalia in North America - sort of like a Hiace and sort of like a VW Kombi, with a pop-up roof.
It is indeed odd how small vans haven't really caught on, given how many hippies there were, and how many Americans love being on the road. They must either get a big campervan, or just a sedan and stay in Motel6.
Different culture to Australasia. There are even smaller vans as well - Wicked Campers.