This could be a Russia-wank in the process of breaking down. They used to own Manchuria, Poland, Alaska+Oregon Country, Anatolia, etc, but they're decaying and bits are falling into the hands of foreign powers.
Let's say Russia has a really great 19th century. They utterly destroy the Hapsburgs and Ottomans in a series of wars, taking Anatolia and much of the Balkans. They inflict limited defeats on Britain and China, taking OTL Pakistan and Manchuria. They expand into the Oregon Country. By the start of the 20th century, they are ready to start enjoying their empire and sitting pretty on the top of the world.
However, they've got a HUGE list of potential enemies by this point. Sometime in the 1920s or 30s, a big alliance of the countries Russia has pissed off over the last century gets their collective shit together and plans to knock the Russians off their high horse. They attack in the 1940s. Russia gets beaten, barely, and has to accept fairly big losses. Large bits flake off of Russia. Manchuria, Poland, their bits of America, etc, all are lost. Russia is by no means out, though. By the 1950s, they've rearmed, and started to develop nukes. Splits in the Alliance lead to a tripolar Cold War, with Uber-America, a loose European alliance, and Big Bad Russia competing for influence. China is the big neutral power TTL, along with India.
This explains most of the Eurasians borders, I think. I think the Americas and Africa could be plausibly attributed to butterflies. Let's say the US wants to imitate Russia and the rest of South America starts banding together nervously after Mexico gets annexed.