Although China certainly had a strong influence in Vietnam between 1371 and 1592, Vietnam was not truly a "Little China" during that period, relative to the smaller nation's much greater subjugation in an earlier era. In fact, by 1371, the beginning of the era under study, Vietnam had thrown off the outright domination of China which had kept the people under the thumb of the Chinese for centuries.
In fact, there is no true way to have a clear perspective on the Chinese relationship with the Vietnamese during the period under question without putting that relationship and that period into the broader historical context. The fact is that if we were to consider the period in question, China, at times, certainly held great sway over Vietnam, although it would still not be accurate to refer to Vietnam as "Little China" during the period in question. However, the Chinese influence in that period simple pales compared to the earlier complete control of Vietnam by the Chinese.
Complete and unquestioned Chinese rule dominated Vietnam from about 250 B.C. to 938 A.D. The kingdom of "Nam Viet" was founded by the Chinese general Trieu Da in 208 B.C. (Florence 10). That event and subsequent Chinese actions effectively placed ancient Vietnam under Chinese rule, although even then "there were major rebellions against Chinese feudal rule in the 3rd and 6th centuries" (Florence 10), demonstrating that the Vietnamese people were no more willing in ancient times than in modern times to bend without resistance to foreign invaders.
The argument that Vietnam was indeed "Little China" during the period in question is severely weakened by this historical comparison. The implication of the term "Little China" is that Vietnam was, in effect, nothing more than a part of China which happened to be separated from China geographically, that the Vietnamese society, state and culture were simply part of China and not unique or separate in any way. Certai...