Not entirely, but a lot of the eastern problems stem from being almost literally being worked to death and not having time to date due to the culture. Such as Japan, you're expected to essentially give your life body and soul to the company you work for. They also don't express themselves as much as us in their languages and have a massive decline in annual birthrates as a result of both and more. Similar, but the specifics are different in my opinion.

Is this a problem in southern / Eastern Europe or just Western Europe, USA, and Asia?

Anecdotal, but I can personally say much less so in Serbia than in Canada, USA, or UK.

I don't think so, you hear the same thing happening in Asia as well.

It makes me think it's a socioeconomic issue.

or, from a different perspective, we're experiencing a population cap, as experienced through cost of living increases. Starting a family is a luxury not everybody can afford.

High quality people may make that choice/distinction, but millions of mediocre childhoods are facilitated through handouts and their requirements without any forethought by those involved.

Really a failure of culture imo.