I spent a lot of my teens convinced of this fact. I spent a unwelcome amount of time looking at the actions of the US in the years leading up too and after the second world war and came to the conclusion that they'd essentially set up a kamazai world economy - which either they controlled, or no one did - Claims of human extinction, however, should always take in too account just how many of us there are. It's hard to exterminate bugs in a house even with a fumigation, and we're a lot smarter and the world is a lot bigger. Out of curiosity when you say extinction do you mean catastrophe or actual bone fide extinction?