Can't speak to the Argentina piece of things, but you're out of luck trying to take a rental from Chile into Bolivia. The tour vehicles used for the Uyuni salt flats trip in Bolivia don't even enter Chile. Passengers are shuttled up to the border and change vehicles because the paperwork for bringing a vehicle across the border is so messy. And I've driven the "road" from Calama to Uyuni. There's no way you want to do it in a rental car, or even a rental 4wd. It is a "highway" in name only.