This is a very tiny model of the Team America Hummer H2. It's only about 6 inches long, and has a fiberglass body. The interior is made of a few flat pieces of plastic glued together with wheels attached (and it can be removed).

I don't believe this particular model was used on-screen in the movie (or at least, it didn't make the final cut).

To get an idea of the scale of vehicles used, here's this little Hummer (which I believe is the smallest made for the movie) sitting on top of the 1:3 scale Hummer body (which is the largest size made for the film at a little over 5 feet):