Subsaharan Africa ITTL. Which is much better off than IOTL. Like I said, South Africa is leading the way with a GDP per capita and a standard of living on par with OTL Southern Europe. Besides, IOTL Oaxaca has a GDP per capita on par with countries like Ghana, Sudan, and Mauretania. So it's not too far off. Whereas Guatemala is just a bit worse off than ITTL, which has it on par with Cape Verde. Meanwhile, again, California is on par with countries like Norway and Switzerland IOTL. So when you ask what happened, it's basically the same thing as what happened economically IOTL.
Anyway, a little something I've been thinking of to tide you over. I've been thinking about what New England's place is in the Commonwealth of Nations, and I think with how much it devotes to education and innovation, it'd probably be seen as the Tony Stark of the Commonwealth: brilliant, and flush with cash because of it (IOTL New England as its own independent country would have the highest standard of living in the world, and it's the same here). So that got me thinking some more, and so I quickly cobbled this together: