I'm guessing that Mr. Derbyshire's Chinese in-laws have been extremely mean to him; else I don't quite get his hostility towards his children's motherland. He should be happy that they'll get to choose to live in the world hegemon no matter what happens during this century. But no, he keeps criticizing the empire.
To his credit, he criticizes the other, as of now foremost empire, the USA. I guess it's this small-town conservatism thing. This dream of ethnically homogeneous, small countries, tied by very strict but widely shared cultural norms, and ruled through direct citizenship participation. Yes, it's kinda nice. There's this bucolic flavor to it; and if we look at revealed preferences, people all over the world pay big bucks to visit those kind of places (Switzerland, northern Italy) every year. To the point, tourists visiting Japan is a booming industry, with over 20 million visitors last year.
But as nice as homogeneous, peaceful towns/countries are; the logic of history doesn't care. Northern Italy was this collection of small sovereign city states. Then they consolidated into a few states ruled by the biggest cities, Milan, Venice. Then Napoleon came with his steamroller and it all went to hell. The fact that Switzerland still exists has all to do with it being a bunch of (back then) unproductive real estate freezing up in the Alps, and not due to its superior government.
Anyway, to the point, Japan. I know Japan. Very well. There's no fucking way in this universe or in any of the infinite universes out there that the 21st century is the Japanese century. Yes, Japan is a fairly pleasant place to live. No crime, by our standards. Very clean; awesome infrastructure. Amazing service by workers so polite they put Victorian butlers to shame.
But Japan is dying. Japan was the first country to stop breeding (and refuse to mask it with foreign workers), so right now it has a 25% old-age population. One in four Japanese are over 65 year old geezers. Who get pensions and consume untold amounts of free healthcare. Who pays for that? Well young people; who haven't seen their salaries raise, even nominally, for decades, mostly due to raising payroll taxes. The money-printing hasn't produced any inflation, but it has produced a bubble in the stock market and prime real estate.
Young people aren't stupid, they see the writing in the wall. If Western populations have been losing testosterone due to getting their balls busted by feminism since the 1970s; modern Japanese have lost the will to live, period. 40% of Japanese are virgins by age 30, men and women. You'd think it's all the lying Western press, fake news. Oh no, I know the place. It's true, people. National decline is a scary thing. Japan is in steep decline.
Oh, but the don't have immigrants! Bullshit they don't have. Try to buy any groceries in central Tokyo and not see a Vietnamese or Bangladeshi kid in a 7/11 uniform. There's 2 million immigrants. There's foreigners everywhere. 2 million in total. Yes, of course, compared to what's going on in the West, that's nothing. Japan has a rational policy. It doesn't take "refugees". It takes workers, on their terms. Pretty harsh terms. Japan pays low salaries and makes people work really, really hard. Plenty of foreigners just won't take it. Japan is very far away, it's expensive, the language is crazy hard, there's little fun to do out there. And the sort of Japanese boss who takes foreign workers (agriculture, low-margin manufacturing and the like) are often nasty, nasty people. The conditions some workers are made to accept would make many Dubai employers blush.
Of course, that's the only way to run an immigration policy that pays for the accepting country. Japan doesn't have an immigration industry. There are no foreign foundations paying for the colonization of the country by hostile foreigners. The government doesn't fund QUANGOs to bring them. It doesn't give welfare quotas to their cities to advantage foreigners over natives. The Japanese have their country, and want to keep it. Yes, they'll take any foreigner who is willing to work for them, without making any accommodation. Japan is their country and they like it as it is. Good for them.
But... Japan is not going anywhere. Don't believe the hype over the recent GDP growth figures. It's all bullshit. Japan is losing 1 million workers every year. The electronics industry is dead. Sharp was bought by the Chinese, Toshiba is bankrupt. The videogame industry is dying, completely outdone by America's. Japan tried to start an aeronautic industry, with the much hyped Mitsubishi MRJ, but the plane sucks and Mitsubishi Aircraft is bankrupt. Japan today can only afford to eat meat because Americans like to drive Toyotas and Hondas. Japan's future is closely tied to America's. As the USA declines, so will Japan. But the USA has the best real estate in the world. You can fill the USA with Mexicans and Africans and they'll still have plenty to eat, if only. Japan though, is a bunch of volcanoes on the path of the Asian monsoon. They can barely feed 30 million people by themselves. Their economic boom only happened because they happened to be an American vassal in a strategic zone. But America will soon run out of money to feed their vassals.
What then? The Japanese century? Hah. In all likelihood they'll be China's bitch in 2 or 3 decades. And China will not be kind to them. The Chinese empire used to be kind to its vassals, giving them vast amounts of money in exchange for pathetic shows of allegiance. But China doesn't have an empire now. It has a micro-managed, internet-connected demotic regime, with hundreds of thousands of people engaging in government PR. Japan better practice their kowtows very well if they want the Chinese people to show them clemency.
So again, let us not lose sight of how the modern world works. Hell, how the world has always worked. Good government is nice. But nations don't live in a vacuum. Foreign policy is as important as internal policy. It doesn't matter how well governed a nation is, if the international situation isn't good. Venice was very nice, nicer than France; Napoleon crushed it. Same for all those nice bucolic principalities across Germany. If your neighbor is big he is going to crush you, sooner or later. This is a fundamental principle of history. To that, add globalized economies today. Hardly any country is self-sufficient today, even potentially. Every single developed country today is an American satrapy. How long will the US be able to afford them? What then? Certainly not the Japanese century. Nor the Swiss century. Gentlemen, there is no Patchwork, and there will never be. The logic of Empire always applies.
Have I mentioned there's a growing community of Japanese converts to Islam? Of course it's still tiny, but it's really funny. And given the sexual market in Japan these days (40% incels, remember), there's plenty of incentives for it to grow.