Christian nationalism is prevalent in the U.S, Buddhist nationalism is prevalent in Myanmar, and Hindu nationalism is prevalent in India. Religious nationalism is a very controversial and traditional tool that is deeply embedded in world history as it has connected the world. However, unlike other countries and even its close countries such as China and Japan, Korea is considered not to currently have a religious nationalism and is rather a country in which all the world's major reiligons, Christianity, Buddhism, Islam and shamanism coexist.

                      -https://www.factsaboutkorea.go.kr/bbs/view.do?nttId=NI_00000000000004161&ln=en

Why?

Shamanism, which was prevalent in Korea has been a more cultural practice than an institutional religion as it was localized and utilized as one of the means for Koreans to endure individual life-related pain rather than exertion of authority. 

Buddhism, one of the major religions believed in Korea, rose and fell with Chosun dynasties. It is correct that kings utilized Buddhism as a political tool to control the common people. However as the leaderships changed very frequently due to political conflicts the people were not entirely oppressed to believe in Buddhism. Buddhism was mostly seen as dynastic convenience instead.

 

Confucianism, also one of the most common and popular religions of the Chosun era, was operated more like a social guideline and framework that provided knowledge for the people of how to behave more than requiring faith for a god they worshiped. Confucianism taught the Koreans about the importance of loyalty towards their family, hierarchy, and life-style.

 

Christianity arrived very late compared to other religions, as Catholicism had arrived in the late 18th century, and Christianity arrived during the 19th century. Christianity also had a historical obstacle blocking its expansion in Korea, as soon after it arrived in Korea the Japanese colonization took place. Christianity however indeed got the chance to thrive in politics after Korea gained their independence in 1945, supported by the U.S Army Military Government in Korea (USAMGIK).

-Additional effects of history, Japanese Colonization / Korean war

• The Japanese colonization performed religious oppression towards people from other religions as a mean to oppress the Koreans, such as hindering Christian and Buddhist practices due to the fact that they "support Korea's independence". The Japanese also coerced shrine worship to Koreans from all religions in order to annihilate Korea's ethnicity (ethnocide). Korea did not have any chance to develop religious nationalism after they gained independence from the Japanese colonization either, as the Korean war initiated in 1950. After the war, Koreans did not worship god but survival, economic growth, and nationalism without theology.
•  

Why does this matter (now)?

 While religious nationalism influences politics of the world, South Korea shows a different historical path that shapes its national identity which was shaped more by cultural traditions, foreign occupation, and rapid modernization than faith towards god. As a result Korea is religiously more diverse compared to other countries. South Korea would be a strong example that challenges the thought that national identity must correlate with a dominant religion as shown in the U.S, India and Myanmar.

 Korea did not develop religious nationalism because its major belief systems were utilized as cultural or political tools rather than sources of respective spiritual identity, and later historical events shaped the national identity of Korea more survival than religious.