Reddit mentions of The Lonely American: Drifting Apart in the Twenty-first Century

I'm not going to spend much time on whether anime is good or bad in it of itself. It definitely seems to appeal to some bizarre (usually sheltered) sorts of people (myself very much included), but I would say that it appealed to them because they were "weird" to begin with, rather than make them weird, and that it fundamentally isn't any different from any other nerdy hobby - comics, video games, sci-fi movies and TV shows, fantasy novels, and so on.

I'm more interested in what your friend is saying about how it's contributing to Japan's population problem. Now, the declining birthrate is a fairly significant issue that Japan is facing, but I don't think anime can be attributed as a significant cause of that. The fact of the matter is that nearly all developed countries have declining birthrates, for a large number of reasons. Japan has a bigger problem with it than the likes of the United States and Western European nations, though, because it lacks the immigration those countries have that keep their population more stable. In addition, the immigrants to those countries tend to be, along with poor families, the demographics with the highest birth rates. Here is just the first article on the subject I found by Google searching "first world countries declining birthrates." Similarly, a lot of first-world countries are experiencing the "lack of interpersonal relationships." As much of society's standards and values move from the family or community to the individual, more and more people are feeling lonely, even when they have plenty of friends, because much of their friendships lack the more permanent sense of belonging given by tightly knit families or communities. The Lonely American is just one book on the subject.

So in short, I don't think these problems Japan has with declining birthrates and interpersonal relationships is exclusive to Japan, much less the fault of Japanese cartoons. Is it making the problem worse? Maybe. According to Wikipedia, approximately 1% of Japan's population consists of hikikomori (social recluses, or shut-ins), and I would think that percentage would be a lot higher if anime were as much of a problem as your friend seems to suggest, so I have my doubts. There are a lot of bad things I have to say about anime, much as I may enjoy it, but I don't think contributing to Japan's population crisis is one of them.

The Nudist didn’t show Sat morn, chatted up a random woman about her car at the laundromat on Sun, got a lot of cleaning done at home, considered opening a Match account but couldn’t pull the trigger, started reading The Lonely American recommended by someone here on DOT (extremely relevant to half my dating issues).

That's a great question. I'm not a sociologist, but even many researchers will tell you there isn't a single answer for the definitive rise in social isolation. To make some sweeping, general claims, it largely has to do with:

• Moving from tight-knit communities to large cities
  
• More Americans living alone (25% of the US population.)
  
• Less involvement in community institutions (church, synagogue, community centers, supper clubs, etc.) – Bowling Alone is a great read on this.
  
• More controversial, but our reliance on technology for connection. We all have a tendency to conflate surface connections with true intimacy, but the size of your network has no effect on your level of loneliness. Loneliness is better understood by a lack of supportive outlets, instead of simply not being around people. Technology can be great for intimate or surface connections, but social media is generally geared toward the latter.
  
  And right! The study you reference might be the General Social Survey from U Chicago. It's really astounding that it's hard to talk about loneliness publicly, considering the former surgeon general labeled it an epidemic. Hard to believe there can still be a stigma about something affecting so many people.
  
  If you're interested in this, two great books I recommend are The Village Effect and The Lonely American. Both have excellent theories and explanations.