I think of the huge countries, Brazil is probably the one with less useless land?

Brazil harshest environment is the quasi-desert plains in the northeast non-coastal region, it rarely rains there because the coast has lots of hills high enough to block rain (thus the coast is very rainy too), but it is not a complete desert (yet... overuse of land in agriculture is slowly transforming it in a desert).

Brazil has no crazy areas of desert, tundra, or other non-fertile areas, the only parts "hard" to live as human are the rainforest (because it is too dense, nothing you cannot fix by making your own clearing) and the marshy area (because to live there you need to figure how to make a floating house or a house that don't flood).

US has the Arizona desert, and some snowy mountains, Canada half of it is just ice, Russia too, half of it is ice, China has a huge desert plus the himalaias, and the largest countries in Africa usually are large because they extend the border to the middle of Sahara because of natural resources, it is not really useful land.

And Australia has that very dry outback where you cannot have proper farming.