1) Who did the map favor? Why? The majority of the land belonged to the United Kingdom followed by Mexico then the United States. The map is basically cut into three major sections (plus Russia's portion at the top of the map and other small portions belonging to other places.) Each section is pretty even, but United Kingdom has more than the others, plus it was also sharing a big piece of land with the United States. Mexico has a solid chunk of land at the bottom, but shares land with others as it goes further into North America.
2) What has happened since? Russia has completely left this map entirely, while the United States has taken territory from Mexico. On the current map, Mexico's territory is only the Southern section of land below the United State's land. Canada's territory is now the United Kingdom's territory, although Canada is still lightly connected to the UK through royalty.
3) Who was affected? Since Russian's land was completely stripped from them, I'd say they're definitely affected, along with Mexico who had half of their territory taken from them. United Kingdom was also heavily affected, although they have land outside of North America now. United States is the only one that purely gained land.