Is it necessary to write "United States of America" in bibliographies when describing the place of publication? I'm from the UK, and currently writing my dissertation. I'm citing several sources from publishers in the USA, and am unsure what the best practice is for writing the place of publication. The publisher is based in Hoboken, New Jersey. I could write it in any number of ways:

Duanmu, S. (2011) ‘Chinese Syllable Structure’, In: van Oostendorp, M. and others (eds.) The Blackwell Companion to Phonology. Hoboken, New Jersey, United States of America: 1-24
Duanmu, S. (2011) ‘Chinese Syllable Structure’, In: van Oostendorp, M. and others (eds.) The Blackwell Companion to Phonology. Hoboken, New Jersey, United States: 1-24
Duanmu, S. (2011) ‘Chinese Syllable Structure’, In: van Oostendorp, M. and others (eds.) The Blackwell Companion to Phonology. Hoboken, New Jersey: 1-24
Duanmu, S. (2011) ‘Chinese Syllable Structure’, In: van Oostendorp, M. and others (eds.) The Blackwell Companion to Phonology. Hoboken, NJ, USA: 1-24

I don't think I can simply write New Jersey or NJ, as I've cited another publisher from Norwood NJ. I'm not sure whether it's necessary to write &quot;United States of America&quot; in any form, as to me, New Jersey is unambiguously a US state (just as I wouldn't need to clarify that London or Oxford was in England). But given that I'm not in the US, is it better to do so? And if so, which form is it best to write it in?
I can't refer to my reference guide for help, as we use the unhelpfully inconsistent MHRA Author-Date system, which varies between just about every resource.
It's a good idea to take a step back here, and think about what the purpose of the bibliography is. Ultimately, it is supposed to allow a reader to unambiguously determine what publication is being cited, and further to help them get a copy of the publication.

In order to achieve this goal, I'd argue that specifying the location of a publisher is in most cases an anachronism. Given there is only a single 'Blackwell Companion to Phonology', which I can find in seconds with a web search, I don't really need to know that the publisher is located in New Jersey. We only still do it out of tradition. Incidentally, a far better way of unambiguously referencing a book is to state its ISBN.

However, bibliography styles may require that we include a location. In your case, you are unable to find a single 'correct' way of stating location for your bibliography style. So I would say, do whatever you want. Frankly, even if one of these is 'correct' under your bibliography style, I doubt anyone would notice, and if they did notice, I doubt that they would care. My personal preference would be towards brevity (e.g. Hoboken, NJ, USA).