Earthquake / Civil Unrest.
I worked for the City of Anaheim about 20 years ago. One of the things they had new employees do was a series of lectures/orientations. The head of Risk Management spoke at one time. He made the biggest impression on me. He talked about how we have a major event (earthquake) on average something like every 100 years in SoCal. And it was past due. So it wasn't a matter of if, it was a matter of WHEN.
And of course after the LA riots...I realized that earthquakes wasn't the only thing to be prepping for.
As far as world wide collapse and crazy wars etc....I don't think that, that is something I can really prep for...and considering where I live...no real way to probably get out and no where to go to. So my preps consist of 30 days of food and water for 4, plus arms and ammunition to defend and a decent place to hole up.