It's an ASB  scenario in which history proceeds pretty close to OTL until the day one Cristoforo Colombo sails west and fails to arrive anywhere. Stuff happens. The lack of American silver leads to an early fall of Habsburg power, Portugal benefits, the development of European modernity is delayed, an alternate *Protestant revolution takes place and leaves Poland and almost of Germany *Protestant while Scandinavia and the British isles take part in a split in the Catholic Church proper: large-scale colonization never really becomes a European habit in a world lacking in areas for settler colonies or an American example. The lack of American silver also does weird things to the East Asian economy and Ming history. Europe never becomes as dominant.
A Great War in the 1930s pits a Japan which never closed off and an early-developing Russia and their various little buddies against a coalition which, through late-German levels of diplomatic incompetence on the Russian-Japanese side, ends up drawing most of the world. Russian and Japanese empires are ruthlessly broken up.
Today, the world is generally at peace, with limited monarchy or bureaucratic technocracy of anti-ideological mode being the dominant forms of government. Atomic power has been developed recently, it's peacetime origins making it much more popular as the "energy of the future": there's a bit of an optimistic atompunk feel about things, albeit with some worries about whether the Chinese will end up as a true global hegemon. There are worries about food security and resource limits: without the Americas and their valuable plants, Europe has had more trouble feeding itself, and agriculture is more intensive and more "urbanized" ("vertical farms" have been in existence for a long time) than OTL, although some pressure is taken off by a more developed Middle East and Africa better able to feed themselves (and in parts of Africa, actually exporting quite a bit of food).
And of course, scientists remain puzzled by how the Lost Continents: did they, in fact, sink? The seafloor dredging (now helped by the first deep Bathyscaphes) seems conclusive, but no mechanism is known, and why didn't the overall sea level change? Many ascribe the event to divine intervention and populate the Lost Continents with all sorts of evil imagined civilizations, some positively Tsalal-ish : others suspect the intervention of Alien(Space Bats)s.
 'If you're wondering how he eats and breathes/and other science facts...''
Nice AU idea, especially how the minorities in OTL Russian Sibiria got their own nations here. Also, Ainu nation? Seems like the Japanese preferred the deportation solution with natives of Hokkaido instead of assmiliating them outright.
Wow, thatīs a cool idea. Imagine a world without tobacco, potatoes, maize, tomatoes, sunflowers and cocoa. Let alone without American cattle breeding, sugar agriculture and silver mining. Which means that the famous Spanish colonial empire never came to be.
Portugal should have gone on a conquering spree of African shore and India. After all, it was already colonising places in Morocco and islands of the Atlantic before Columbus ever finished high school.
Well, they did control much of the southern African coast for a while, along with Indonesia and a lot of islands and coastal cities in India, China and SE Asia and such - they just lost most of this to the French and English later on. Portugal in the 16th century really doesn't have the tech and organizational edge Europeans had in the 19th century - they really can't run wild in India any more than they did in our world.
The lack of Pacific Islands make the map a lot more sparse than you would initially think. It's funny; most mapmakers don't give a lot of thought to the Pacific Islands, but once they're gone, you really notice it.
Awesome map, BTW; have the inhabitants of TTL given much thought to the possibility of space exploration?
Also, can you do Bod next? That's my favourite of G-M's AHTGs.
Given that one would typically associate less population with less advanced science and technology (fewer minds contributing ideas and concepts), is there a larger emphasis on science and scholarly pursuits in TTL to compensate?
Also, are planned economies more central to this world than ours? It just seems to me that a world more likely to suffer from resource shortages on a more frequent basis than OTL is more likely to have higher levels of government control of resources; just my thoughts.
Well, that's part of the technocratic/atom punk air of this world: scientific R&D are pushed pretty hard. And the people shortage is to some degree compensated that much of Asia and Africa are more developed than OTL, so are better able to produce scientific research than their OTL-equivalents. They're still about 50-60 years behind OTL technologically. And yeah, governments do tend to keep closer tabs on important resources (on the positive side, this has led to an early government support of environmental initiatives, to preserve watersheds, prevent soil erosion, etc., etc. Balancing sustainability vs the problems of keeping everyone fed is a hotly debated topic, especially with populations still growing briskly in much of the world.)