The history of other regions and civilisations serve no such similar purpose and have been ignored.
Before pointing fingers at the West, does Iran take an extremely detailed view of its Persian History, that would not go well with Islamic Iran.
If a country wont look at its history why do expect others to look at that country's history?
Russia, not sure what you refer to here, but few written documents and sparsely populated areas explain the lack of historic research much better than american intent.
As for central asia, which civilization are you talking about ?
The sad reality of history is that having contemporaneous writings by the people involved adds a lot more color and detail to history than archeology, so people are naturally more interested - there's more that can be known!
That seems a very US-centric viewpoint. Plenty of Western archaeologists aren't Americans. For many European countries, the Roman Empire is an important chapter of their own history, so it is unsurprising that archaeologists in those countries would be interested in it-and their interest has nothing to do with the United States. (Even many of those parts of Europe which never were subject to Roman rule were nonetheless enormously influenced by Roman culture, through the spread of Christianity.)
The reason we know so much about Rome and Greece is that we have a lot of written material - histories, literature, poetry, letters, laws etc. Archeology is a relatively new science, while history (the study of written accounts) have existed since antiquity.
History is not just a question of what happened, but also about the effect of what happened. For example the Egyptian or Sumerian literature and philosophy might be just as magnificent as the Roman, but since those languages were lost it simply did not have the same effect on subsequent culture as Rome had.
While the Japanese Royal Family claimed descent from a God.
In other words, the Danish royal lineage descends from both Norse and Greek gods.
Why would people learn about some random kingdom which was a vassal under British rule?
My comment answers why you did not hear of them.
I remember looking for books on the history of Japan a while ago there. Fifty books about the glorious defeat of Japan in WWII, a few hour long books on their complete history, and a great courses lecture series.
My (WASP) uncle learned Japanese and moved to Tokyo because of a personal interest in that specific culture. I'm happy for him, glad he had a good experience. Should I now chastise him for not doing that with other cultures?
This `personal interest == bigotry` attitude is a problem.