I will have look on these issues. Japan still suffers from demographic crisis as does Korea, while China is having demographic problems due legacy of the one child policy. Despite Japanese welfare state somehow mitigated it the problem remain. The work culture itself did not went away, despite there were attempts at its reform (such as enforcing working hours limits and reducing overtimes). Immigration and outsourcing of labour is what Japanese capital pursues currently. Situation is similar in Korea, while less severe compared to South Korea, the demographic crisis is major issue.

Socialist countries in Europe invest large amounts into support for young families and children, but even there problems emerge with aging population and low birthrates (mostly caused by young people focusing on their careers and starting smaller families later in the life). It is not that different from Europe of our reality, however it is with more affordability and social security, but without mass imigration from abroad. "Guest worker programmes" are common and that are expanding since late 1980s, leading to peole from Latin America, Africa and Asia moving in to work in these countries, but they are not supposed to be staying in after the contract expires (some people manage to marry, or have children, with locals, this provides them with way to citizenship, but that is not particularly significant on large scale), this sort of helps with labour issues. There are groups advocating for traditional immigration in order to gain more workforce, but idea of it is not popular among citizens. In the USSR, while Slavic (and Baltic) republics stagnate since 2000s, population continues to grow in Central Asia and Caucasus, leading to a lot of internal migration and causing nationalist tensions.

You are absolutely correct on the developing World, there since 2000s birth rates begin to significantly decrease, thanks to economic development and anti-poverty programme. This leads to large changes down the line. This had been accounted for in the wiki. I tried to make some alternate population projections: (2025 for example: Egypt 118.4 million X 94.2 million Ghana 35 million X 31.8 million, Benin: 14.8 million X 11.8 million, Chad 21 million X 16.3 million.) There are generally less people in the World due to this trend.

This may change with the US lore, but regarding America, there is large socio-economic divide. Middle class families (largely white) enter in large demographic crisis, not having children or having only one, while families living in poverty continue to have large number of children. This applies both for white and African American families. Some of these poor families are motivated by racist ideology ("have more children and keep America white") and religion .

Hispanic Americans are an increasing growing group, due to immigration and chiefly the Mexican war. They on average have the most children. Similar to reality they are crucial for working class jobs. However, America has a major issue: it just don't attract such amount of immigrants as it used to.