As a native speaker who has done a fair amount of professional writing, I would either intensify immediately before the key idea, namely “none of the Americans.” For example,
I met not one of the Americans, …
A good alternative is to repeat the negation immediately after completing the relevant phrase. For example,
I met none of the Americans, not a single one, …
This is a matter of style and so at least partly subjective, but, although breaking up a key component of thought is an admittedly frequent occurrence in speech, it makes for hard reading and so should usually be avoided. Furthermore, intensifiers like adjectives work most effectively in English when adjacent to the thought to be affected. Word order is so important in a language with little reliance on inflection.