I actually don’t really see this as much. When I was studying about China and Taiwan at the undergraduate level, I would say about half the sources were written by Taiwanese and Chinese people. This is also true in my experience for the Philippines and Viet Nam. One thing that should be mentioned about Chinese sources, and I mean to say modern mainland China (not Taiwan), is that, frankly, the quality of scholarship can sometimes be subpar because of censorship issues. Basically, research published in China has usually either been censored by the government or has been self-censored out of fear. So research from the country is used, but it has to be used carefully. A lot of the great Chinese historians that get cited outside of China (including ones I know personally) are usually scholars who moved out of China and are based at a university somewhere else, away from censorship. In fact, it is sometimes quite the hurdle doing research in China as an outsider because of issues with the government. These are things that I know from my contact with historians of China and of Viet Nam (another authoritarian regime), but it’s also the subject of research, such as here. Also, a not-insignificant amount of research is actually done in Taiwan because the Guomindang took a lot of historical records and artifacts with them when they escaped to the island. Basically, a lot of primary sources actually are also in Taiwan, not just China. Of course, research on China and Taiwan by Taiwanese academics is great quality because of lack of censorship in Taiwan and a lot of it is translated into English. They still face hurdles doing research on the mainland though. This problem does not exist in the Philippines on the Philippines when research comes from reputable universities. Most of my sources come from Filipino historians.

At the university undergraduate level, this is largely an accessibility matter. History departments, as with many other departments in American universities, are under perennial pressure to 'be relevant'. One of the metrics university administrators often use to assess 'relevance' is enrollment numbers in a department's courses. Leaving aside the problematic nature of funding departments based on fuzzy metrics like this, this situation creates an obvious pressure on faculty to write broadly accessible curricula. If you're teaching, for instance, a 100 or 200-level Russian history course, a Russian-language reading list will immediately shrink the pool of students who are able to take the class quite drastically. Relatively few of the important works in other languages' historiographies are translated into English, certainly not enough to base a curriculum on I would suspect - especially not in 'harder' languages like Russian or Mandarin. Faced with this, most curriculum writers tend to default to English-language reading lists. I know that at my undergrad (where I was a history minor, not a major, so caveat here) there was an understanding that history majors would be graded on a different scale than students taking history courses as electives. For example, a history major with a focus on Mediterranean history might be expected as part of her course of study to become fluent in Italian, and also then expected to make use of Italian-language sources in related courses. The history department at my school was quite small, so it was easy enough for faculty to keep track of these things; I do not know if larger departments behave similarly.

Now, at the 'professional' level, yes, it would be considered very poor form to write Russian or Chinese history without engaging with those countries' scholarship at all. In my flair field, for instance, there was a real revolution in English-language scholarship in the late 1980s and then moreso the 1990s, as American and British historians began to engage much more seriously with Russian-language sources and historiography. The bibliographies of major English-language works are now full of not only Russian archival sources, but Russian secondary sources.

What historians choose to research is as important as the history they write about. This is important because it is also why we choose histories closer to our own culture and society over those elsewhere. They are closer to the cultural zeitgeist within our own system and easier to answer the inherent question we are asking about a specific history. Fundamentally this is why often scholars pick histories from our own societies over others, because they more closely answer the framework of questions we have about a specific topic.

To use an example from my own studies of the Soviet Union the schools of thought all center around specific ideas that other countries' historical work would not fit within. For example, the first breadth of historical work was done surrounding the fundamental question looking at how the Soviet Union was bad, focusing on misdeeds and digging into how corrupt the system was. The fundamental question driving a lot of these early scholars were how the system could or would fail in the future, and comparing it to other failed regimes. These were known as “Cold War Warriors.” The subsequent generation tended to reject their thesis, but wrote in opposition to that initial premise. These “Revisionists” were contrasting and rebutting against the Cold War Warriors, not devising new trains of thought or expanding outward into new forms of history. The history eventually did branch out, with the focus on social history being imported into the United States. Without going into the post-Cold War historians these two camps had a discussion and were looking at the Soviet Union’s history from an United States lens. Within the framework of “The Soviet Union is an Evil Empire” and “Maybe we should rethink this” the use of sources or scholarly work outside of this dichotomy is seen as irrelevant or unimportant unless used to buttress the ideas being espoused by either of those two camps.

To frame it another way entirely, think of history as a discussion of a bunch of collected scholars. They form in a group and tend to focus on a couple “major questions” and revolve their discussion on what has already been said and spoken in their group. There may be another group from the country they are studying, but they themselves are discussing an entirely different “major question” and using the ideas discussed previously to continue their discussion. There may be some borrowing of ideas from either group, but both continue to discuss their ideas independently from each other. This is because inherently they are asking different things and the ideas may not be compatible even if the subject is exactly the same.

The other major issue is a certain level of imperialistic or chauvinism in academia towards native history. For the longest period the American historians would not trust any Soviet historian work on any subject because it would be “wrong” or “untrustworthy.” This is not just a communist thing, however, as that same level chauvinism continues till this day now that all history is now “too nationalistic” or too “pro-Russia.” Some things never change.