The comparisons the author makes are on a scale much larger than the diversity of the USA.
If you cannot see this I cannot work out how to tell you, except perhaps to suggest that you and live and work on the other side of the world.
Have you travelled outside of the major cities, or even > 50 mi away from an international airport? I've been traveling the country for a living for the last 15 years and the diversity is staggering.
If the USA is so homogeneous, what nation on this planet would you consider more diverse?
don't understand your last sentence. been in china/hk, there's a lot less diversity there, at least racially. are you using diverse in economic terms? gender? age? consumer habits? religion?
This does not require the destination to be diverse, simply very different from the USA.