I was thinking that there is a period of instability in Latam, with realignment and refugees etc, and that at the end of it, they attempt to create a new UN based in Rio. The remnants of the us navy mainly went to the Caribbean, and I'm pondering having Hawaii damaged but not as totally as much of the rest of the us, with a government in exile that lacks much reach. They build new ships but to save vitally needed steel etc they use Amazon timber to build wooden hulled ships; theres no real chance of meeting an armoured ship so wood with metal plating is sufficient. The ships are steam powered for propulsion with diesel generators. I'm picturing three armed ships, three colliers, and a supply ship that also carries a pair of biplanes with both land and water landing gear and a set of helium balloons to carry instrumentation and camera gear on a tether over dangerous areas, and they carry a company of marines armed with bolt a ton rifles, mortars, and a couple of ww2 era machine guns. The government of Hawaii still claims authority over the us, but has no means of enforcing it so is grumpy about the expeditions and demands to have ambassadors aboard them. Australia is host to large numbers of British survivors as well as more American ones including originally diplomats and politicians, and that American group claims IT is the government in exile, so the un doesn't let either go. The British retain st helena, the Falklands, a few other islands, and maybe even Bermuda, as well as uk survivors being part of the Caribbean communities. The french have guadeloupe and a couple of others too. The dutch are basically all in the Caribbean. Things in latam aren't great, theres even more slums, more violence, more poverty, more disease and crime, but it still resembles civilisation at least. The new un wants to show its reach and pro activity, so funds several expeditions. Over the course of these they map the devastation, survivors, and true course of events. Think post apocalyptic semi steam/dieselpunk meets captain cook. Of course the tragedy is that humanity is still fighting, still plotting, still putting narrow interest over global good.