It's called sarcasm. Japan never had that much manufacturing capacity, nor did it have a strong enough army to protect its interests from US, that's the whole point.
Japan's decline is two fold. One. its population size and limited natural resource means its technological development simply can't keep up with the likes of US, USSR and China in the long run. For example, Japan, once known as leading expert in robotics, has fallen behind in the recent years to the point that during Fukushima incident, they have to rent remote control robots from US and China. Don't get me wrong, they are still very strong comparing to the rest of the world and still top contenders in many fields, but anyone who went to a lot of top engineering conferences in the recent years will tell you that there is less and less Japanese presence each year.
The second reason is that japan simply don't have the military power to fully protect its economic development. While all-out open war between major powers have ceased since the conclusion WWII, regional conflict and alternative battlefields have persisted and even expanded. Economic warfare is a prominent example. Today, global economies are close knit and depend on each other to function and an economic attack is one of the most effective method to cripple an opponent. The spoil of the war from such an attack can also be enormous.
How well a nation can resist such an attack heavily depends on several factors. The first one is the available resources. For example, during 97 Southeast Asia financial crisis, although Thailand and Singapore have decent control over its own economic, they simply don't have the foreign reserve to fight off a determined attack from Wall Street. In comparison, Hong Kong managed to fight it off successfully since the combined reserve of Hong Kong and mainland China is way too big. In this regard, Japan is doing pretty good, since it has the second largest foreign reserve on the planet. (Second only to China)
The other factor, however, is the amount of control over its economy. For example, during 97 crisis, the financial attack avoided mainland China entirely. The reason is that foreign influences simply doesn't have the same pull there. Basically, if the Chinese government says the stock price has to be below a certain level (so not too much money flow into there), you bet your a$$ it is going to stay there. The other example is Russia. While the 97 financial attack targeted Russia and managed to make some progress in the bond market, the Russian government simply announced that the bond is going to void (it is more complicated than that, but the effect is on the mark). What are wall street going to do to Russia in this situation? Not a thing. You can't invade it since it got the biggest nuclear stockpile on the planet and you can't prevent its business because all Russia does is selling natural resources and you can't prevent them from doing that because, again, their military is way too strong. In comparison, during Plaza accord, the Japanese and Germans basically rolled over and gift-wrapped themselves to US, UK and France. (The German involvement is another long and complicated story, suffice to say, there is a reason Germans are so keen to keep EU together)