Seriously have this conversation several times a year. People really think Greenland is almost as large as Africa. I than state that we can fit these countries into the area of Africa and people are shocked.
BTW US is the third largest geographical country in the world.
Edit: My favourite being an, apparently serious, assertion by an HN user than Europe would fit in Texas... :-)
http://www.texasmonthly.com/daily-post/how-big-texas-compare...
the last line might help people understand why people compare these things:
"If you’re the right kind of nerd, you can probably do this forever and not get bored"
[NB Note the sweeping generalisations - I know fine well that there is a lot of cool stuff in the "middle" of the USA as well as lots of fascinating stuff round the periphery of Europe - I'm from Scotland!]
My brother's father-in-law, while lecturing me how we younglings don't know nothing and have terrible education, insisted that Iran is in Africa and full of arabs.
I think it works to show how big Africa is.
But yes, if you compare countries, you can take comparisons further, and it would be more practical.