> Why call it reverse culture shock? It's simply a realization that the United States not the best country in every regard.
That's completely not it at all. Culture shock is what happens when one visits another country and realises that certain things one takes for granted aren't, and other things one thinks are negotiable aren't. It's the same phenomenon which young historians have when they first read of a technologically advanced, trading culture which also casts every firstborn child into a furnace (e.g.).
Reverse culture shock is the same phenomenon, when one returns back home. It's caused by the fact that one has assimilated to one's guest culture to some extent, and upon returning home … one finds that certain things one had grown accustomed to taking for granted are not, and other things one had grown accustomed to thinking negotiable are not.
An example is the wide variety of cereals in American groceries, or the limited variety of organ meats. If one has grown accustomed to just buying 'müsli,' and one suddenly has a dozen different varieties, one claiming to be good for keto diets, one claiming to be vegan, another gluten-free, another paleo — that's a culture shock. If one has grown accustomed to making kidney pie, then returns to America and must make a conscious effort to source kidneys — that's culture shock. If one has grown accustomed to horse or whale, and returns to find that they are illegal — well, that's culture shock too.
It's not about better/worse; it's about different.