Lookit what Funimation‘s sent over! Man, they’re super nice. :D
Hetalia: World Series is the third installment of the worldwide phenomenon of Axis Powers Hetalia but is considered a separate series from the previous two seasons. It is based on the web comic written and drawn by Hidekazu Himaruya and depict countries as pretty boys (and girls) and their interactions with one another in a mostly 4-panel comic format.
The setting ranges from ancient times to the modern era but started out mostly as a comic poking fun at Italy during World War II.
The name itself comes from the combination of the Japanese word hetare ([cutely] “useless”) and “Italia”. TL;DR: Hetalia = Useless Italy.
World Series pulls away from the topic of the two World Wars because the comic became more more about silly antics rather than the loose story of Axis vs. Allies. Because of this, there is a clear distinction between the two series and is treated as such even though it contains the same sort of humor and features the same cast.