We know how bad things were in Europe and East Asia because written records survive which describe the crop failures etc. We don't have records from that time period from Africa or South America. All we can do is assume that people there suffered as well, due to the global nature of the problem.

Sometimes people get left out of historical narratives because there just aren't any written records. You can make assumptions, or you can try to make stuff up, but an intellectually honest historian is also likely to just say "we can't know."

In contrast, archaeologists will try to make a case for how hierarchical a society was, or whether it was male-dominated, or what kind of religion it had, on the basis of a few tombs belonging to "high-status individuals" and a couple of pieces of pottery. It's always a bit of a stretch. A lot of what archaeologists believed about prehistory. especially migrations of people groups, has been overturned by genetic studies in the past decade. David Reich wrote a good book about it several years ago, which is probably itself outdated now due to the pace of discovery in that field.