How can I rescue or improve Why wouldn't Japonification happen to US, except the US's higher birth and immigration rates??
You were given a few recommendations in the comments already. Your question is basically just asking "why might Japanifcation not happen to the US economy." It would be good for users who look at the question to know what you mean by "Japanification" beyond just a general stagnation of markets and low bond yields. Here already is a major problem.
The conditions that affected Japan's economy were to some extent unique to Japan. So what are you asking when you look for reasons that Japanification might "not happen" to the USA? Why is it a binary matter of either Japanifcation happening or not happening? The reality is that America might take on some characteristics that are similar to some history of Japan's stagnating economy, but not all of those characteristics. So how are readers to distinguish between what counts as "Japanification" and what counts as some characteristic being too far from that?
One of your article links is also paywalled and I cannot access it.
I think a way to make the question more amenable is to keep things more tight like so:
1.) Define "Japanification". Are you referring to the "Lost Decade" for Japan from around 1991 to 2001, or the broader period of the "Lost Score" that lasted throughout 2010 as well that some scholars refer to? The period being considered usually reflects a different emphasis or scope of characteristics that we're looking at.
2.) Define what aspects of the economy you are specifically concerned about in this question. Inflation, asset pricing and bond rates, employment, worker productivity, exchange rates etc. All these things come to mind when thinking of Japan's period of general economic stagnation.
3.) Ask for more than people's general thoughts on what factors might influence America's future economy. You have to narrow what you're looking for to avoid getting just opinions. Do you want scholarly articles comparing Japan and America's economies from economic historians? Do you want a prediction based on a specific macro model? Etc.
Honestly part of me feels like a lot of questions you ask are just way way way too broad. Like you'd need more than a thesis paper to answer your question. In those cases, narrow narrow narrow your search, not because it's ideal, but because we have to be practical.