Heather Cox Richardson
This simple graphic depiction of France, England, Portugal, and Spain from 1800 to the present strikes me as a useful way to start a class on modern world history. It could also work in a class on colonial or modern American history—less so for a nineteenth-century course on the U.S.
The growth and conflicts and jockeying of the dots are interesting enough, but when the video gets to the 1960s, the explosion is so dramatic any student can see just what a world watershed the mid-twentieth century was.
For a single country, see also this animated history of Poland. HT to Ralph Luker at HNN