Iguazú sits in the subtropical north-east, near the borders with Brazil and Paraguay. Ushuaia is on the Beagle Channel in Tierra del Fuego. In a straight line they are about 3,400 km apart: almost exactly London to Cairo, or a little further than New York to Salt Lake City.
There is usually no direct flight between them. The practical route is back through Buenos Aires, often with a change of airport, and that makes the journey a full day: hotel to hotel, ten or eleven hours.
What a week actually looks like
Seven nights, four places: Buenos Aires, Iguazú, El Calafate, Ushuaia. Count the moves. Even in the quickest order there are four journeys between regions, two of them full days and two of them half days. That is about three of your seven days spent on the move, before you count the long flight in and out of the country.
What is left is roughly a day in each place: a morning at the falls, an afternoon at the glacier, and a boat trip if the weather holds. You will have seen everything through a window.
What we suggest instead
In one week, choose a north or a south. Buenos Aires plus Iguazú plus a night on an estancia is one excellent week. Buenos Aires plus El Calafate and El Chaltén is another. Save the other half for next time. Argentina is not going anywhere.
Try it yourself with the distance check: put your list of places in, and see how many days are left for actually being there.
