I would break up this question into one empirical question and two theoretical questions.
I would start with the empirical question of wether this is the case at all, and, if this indeed is the case, where and when it holds true. My experience tells me that Western philosophy does not always dominate over non-Western philosophy in teaching. I studied philosophy at Moscow State University from 2000 to 2005, and I had multiple courses on ancient non-Western philosophy (Egypt, Sumer, Akkad, India, China), Medieval Islamic philosophy, Byzantine philosophy, Russian philosophy. Later, at various European universities, I attended courses which included contemporary thinkers with a non-Western background such as Edward Said, Homi Bhabha, Gayatri Chakravorty Spivak, Arjun Appadurai, Frantz Fanon, Walter Mignolo. I then went on to teach courses on them myself. The question of whether non-Western philosophies are taught alongside Western philosophies is an empirical question, and it would be interesting to collect some systematic data, for instance by analysing the syllabi of a large selection of different kinds of universities worldwide over an extended period of time. One can start this study by analysing data from opensyllabusproject.org.
There could be also two conceptual questions which we need to answer if we want to answer our empirical question.
The first conceptual question is about how we define as “philosophy”, “Western”, “non-Western”. There have been so many debates around the very term “philosophy” that I am not sure we can find or construct a definition which would satisfy everybody. For a selection of approaches to this question, you can look at these works:
- Deleuze, Gilles, and Félix Guattari. 2014. What Is Philosophy? Translated by Janis Tomlinson and Graham Burchell III. Columbia University Press.
- Gasset, José Ortega y. 1964. What Is Philosophy? 1st American Ed edition. W. W. Norton & Company.
- Heidegger, Martin. 1956. What Is Philosophy? New Haven, Conn.: Rowman & Littlefield.
- Nagel, Thomas. 1987. What Does It All Mean?: A Very Short Introduction to Philosophy. 1st edition. New York: Oxford University Press.
- Russell, Bertrand. 2015. The Problems of Philosophy. CreateSpace Independent Publishing Platform.
There are many more books like this, and many of their answers are not only different, but they are incompatible. Heidegger perhaps would say that Dostoevsky is a philosopher, but Russell would probably doubt that Heidegger himself can be called a philosopher.
The same holds true about the concepts “Western” and “non-Western”. Where does the line between them lie? Take Averroes, for example, who is known today as one of the greatest commentators of Aristotle. He was born in Córdoba, Al-Andalus, Almoravid Emirate, which is Spain today. Is he a Western philosopher? Or Edward Said, who was born in Jerusalem, was a citizen of the USA and lived there for decades and was inspired by Foucault - is he a non-Western philosopher?
The second conceptual question is why this topic is important at all. Some people argue that the search for non-Western philosophy is counterhegemonic, liberating, post- or decolonial, subversive. Yet if we consider Said’s point that the very notions of the “West” and the “East” are deeply problematic, that they are products of the imagination, that they are produced by power relations and are not substantiated by real differences or empirical entities, then why should we take these problematic concepts as the basis for the questions we ask? Perhaps we should challenge our own categories, and through this we can develop more diverse and inclusive syllabi that span a number of different categorizations beyond an imagined "East" and an imagined "West."