They are Ford trucks
Photos of UN missions all over the world usually show dozens of UN vehicles on a site. There are a surprisingly large number of American companies in the midwest and farther west that do medical conversions of chassis. No doubt Congress has made sure contracts for UN vehicles are shared by Americans. There are many, many UN APCs too, probably also some from American manufacturers.
I’m surprised we haven’t heard from a FReeper who might work for one of the conversion companies.