Ozz Caravans in US?

Probobly because the demand for a serious offroad trailer here is actually very very slim. We have enough roads in the United states that you can get close to just about anywhere for a base camp, then use your tow vehicle to get where you want, unlike Australia and New Zealand where there are very few roads. The cost of these offroad trailers is equal to a pretty nice motorhome and faced with a choice of which, most Americans would go for the motorhome, or spend much less on a mostly capable TT or truck camper.