That's one of the problems of our current mercator projection maps. It's impossible to show the scale of things from a spherical (almost) object on a flat map.
It leads to loads of anomalies. Such as equatorial south America and Africa looking a lot smaller then they are and Greenland looking massive even though it really isn't
Also Russia and Canada ARE the two biggest countries, but Canada looks gigantic compared to the United States and it's not, it's only slightly bigger.
Also due to it being sort of close to the equator and not near any other significant land masses, the sheer scale of Australia isn't quite shown. One fact I learnt last year that still blows my mind is that Australia is wider than the moon.