If you're trying to compare country sizes, figure out travel times for your book (or vacation), or explain to visitors why they can't pop from NYC to LA for lunch allow me to introduce you to the handy dandy tool that is TrueSize.com.
If you're trying to find where I live on the map, neither South Korea nor Republic of Korea work. Use plain Korea and you'll get the country that has Seoul in it.
If you want to blow someone's mind, show them the USA compared to Africa or Alaska. Both tend to throw people for a loop.
Egypt is a fun one for Americans. Egypt is as large as the four corners area (UT, CO, AZ, NM) combined.
@LianaBrooks It does blow my mind how huge the continent of Africa Is, and how many cultures/languages/countries/ecosystems are there. It's wildly diverse. I wish I could visit one day.
@janallmac It's on my list of places to go. I have a friend in South Africa who keeps trying to get me down there. But I haven't made it yet.