[yongjik]

It's less about being the dominant language and more about sharing the same writing system (the Latin alphabet) with most of the world. So, however a Vietnamese name is written, since it's already in Latin characters, the characters are imported verbatim (well, usually diacritics don't survive, but what can you do).

The opposite extreme would be cases like Korean, with its own writing system not used anywhere else. Therefore, once an American name is written in Korean letters, there's no ambiguity in how to read it. So Los Angeles is 로스앤젤레스 ro-seu-aen-jel-le-seu, and everyone who can read Korean knows exactly how to read it.

Except... how do you determine which spelling to use? The sound systems are so different that there are usually no clearly correct matches. Also, how do you really know how these names originally sounds? Should Nevada be read with a long "a" or short "a" in the middle? You see a name Charles in an article, is he an Englishman or Frenchman (with different ch sounds)? Should we consider Einstein a German physicist, or an American one?

Two book publishers make two different choices, and you end up with the same people's name written in two different ways.

So, basically, there's no easy solution. You either pay the cost when you're reading (as in English) or when you're doing the transliteration (as in Korean).