Just in case: it's not the "Man in the High Castle"! ;) -- which was published much earlier.
This science fiction story (may have been a novella), from what little I recall, involved the aftermath and description of at least a partial occupation of the US by an Asian nation (not certain if Chinese, Japanese, Korean) and resistance/life under occupation. The technology and setting, I believe, is typical 1970s-era (i.e., no spaceships/laser pistols).
This was very probably published in the 1970s, definitely before 1978, and is a relatively obscure title as I have never seen it anywhere (I might not have recognized it if I saw it though) - not that I've been looking for it but I read SF a lot and scan titles and lists of sci fi books from different eras frequently). I seem to recall it being a bit grittier and more adult (some sexual content) in tone than a typical sci-fi novel for teens.