My thoughts as I kept reading:
[except for the very first point, my other nitpicks don't really affect the book significantly, they point out some personal issues]
>A narrative of japan's involvement in the Vietnam War,
Not that there was much involvement from Japan anyway (especially compared to some other Asian countries - e.g. Korea and Singapore, maybe Taiwan as well - who went out of their way to actually support the U.S). AFAIK they just hosted some U.S bases and provided supports of some sorts, partly to benefit themselves by capitalizing some money, but that's it.
>This task is an important one because historians are increasingly coming to recognize that the United States intervened in Vietnam after 1950 mainly to protect Japan.
Wut? This is like saying you are stationing in West Germany and protect it from Afghanistan by intervening into the latter. Seriously did whoever espouse this even check the map and see the position of the two countries? Not to mention even though Japan was war-torn back then, I'm pretty sure they could have fended for themselves.
There are several later portions which raises brows as much as this one for the same reason. But let me digress.
>> Introduction
I'm afraid I have to take the passages that talk about U.S's popularity in Japan with grains of salt. Not that I doubt the premise of U.S's popularity in Japan, I do have skepticism over the periods of time and the details (not to even mention these seem to be valid only under some specific contexts). Let me just say that anti-Americanism and love for American culture don't have to be mutually exclusive (cf. Richard Bellman's autobiography on some accounts of Japanese attitude, it doesn't have to be related to the Vietnam war). I do concede the war did tarnish U.S's worldwide reputation (in countries whose media cared about it, not just Japan). Just saying that having your rep tarnished isn't exactly = being hated or liked less.
>By 1973 only 18 percent of those polled listed America as their favorite foreign country, in third place behind Switzerland and France, and 13 percent now said they disliked the United States. Surveys of this sort tell little about the United States, but they reveal a good deal about how ingenuous and idealistic most Japanese perceptions of America were before the mid-1960s.
No they don't reveal anything at all.
>Very few Japanese had much taste for communism or wanted the communists to win in Vietnam, but progressives and conservatives alike were haunted by memories of how the Japanese armies had bogged down in China during World War II as they watched the Americans fight Vietnamese guerrillas on TV.
So many issues in one sentence of assertions. Nothing glaring significantly (you can't fault sentences that are neither right or wrong), just saying portions like this is why I find this book to be very bogus.
By the end of the Introduction I see two issues: the sure tone (despite bogus contextualizing), and the tendency to conflate claims (mostly political talks espoused by the actors) with actual intentions. The book reads academic and dry but is filled with mostly the latter, and politicking. Banal to say the book provides no more detail than some Japanese protested and those in the government... kept doing their jobs - but I know of no better way to describe.
===
I have no takeaway from this book. This is not a topic that merits more than several lines in the first place, let alone a whole book - [for reasons, check out my first point again].
A decent book for something written in 1980s and for what it's worth.