If you visit Korea, especially around the time of one of the major national holidays, you may come away with the impression of Korea as a very nationalist place. The people are very proud of their country. The flag is aways flown on national holidays, especially ones which commemorate national independence. However, as Professor Andrei Lankov shows, the idea of Korea as a nation is very new. Even the word for race, namely minjok (民族), is of fairly recent provenance, dating back no earlier than the late 19th century.
You can read his post here.
At the same time, I would hasten to point out that the idea of Italy or Germany as unified countries is likewise very new. At the time when Martin Luther was causing controversy in Eastern Germany, scholars simply did not write in their vernacular languages. The language of scholarship was Latin. It would take a great deal of time for German and Italian, for that matter, to become respected as languages in their own right and ones fully capable of expressing scholarly work. Italy unified in 1870. Germany united as an empire in 1871.