Challenge: Make sure that, by 2014, the world's population stays below 4 billion, and no country exists that is more or less larger than OTL Italy (~300k km^2/~100k mi^2).
However, you cannot simply have nuclear warfare annihilate the world's population, and diseases are out of it too.* Anything out of humanity's control (asteroids, solar flares, etc.) are no longer a viable option either.
POD after 1492.
Why? I've noticed, and I'm sure other people have as well, that the Post-Apocalyptic genre is becoming more and more prevalent in every form of media, from comic books to movies. However, either the cause of the apocalypse is not examined (perhaps justifiably so, Cormac McCarthy), or
it's zombies.
However, causing an apocalypse
without nukes past 1900 seems implausible, and before that disease would seem like an obvious option. So, let's get rid of those.
Note: this is a
challenge. It's supposed to be hard.
*
Disease can help, if you really want it to. Just don't want a super disease wiping out the entire planet.