In Korea, though, all is not clear. Initially they were sold out to the Japanese by Teddy Roosevelt (backed by the Progressives, then unaccountably affiliated with the Republicans rather than the Communists).
On and off through the early 1900s up to just before the Great Depression the elements in Korean society who had collaborated with Japanese occupation moved in and out of American society with ease. Sometimes they were in the Koran occupation government and sometimes in opposition to the government. Rhee was in this class of people, but he wore out his welcome and ended up in the US from about 1928/29 to 1945.
His experience from the time of the Japanese occupation until 1945 can be interpreted in a variety of ways. There are many sites on the internet that present nearly every viewpoint possible. One consistent standard is that pushed by the North Koreans to the effect that Rhee had always been an "American puppet" even back in the 1920s! This seemingly strange notion is based on his interaction with the Progressives in that period. It's possible North Korean propagandists never realized that there were 2 different Roosevelts, from different branches of that family, and that they were in 3 different political parties (the Progressives can be considered to be a third, but otherwise unelectible political party with both fascist and communist tendencies).
Rhee was at Princeton University when he was selected to head up the UN Mandate government in South Korea. When he went back to Korea, he moved classical conservative elements into government. These were the few remaining formerly titled nobles, top level collaborators with the Japanese, and so forth. They were just the folks you would expect to see take over if Rhee were actually a Japanese collaborator in his earlier career in Korea (before he went to the US permanently). The people Rhee froze out of the new government fled North. This included most non-communist anti-Japanese political elements.
I opt for the explanation that Rhee was among the class of Koreans who had favored Japanese occupation, and later on favored US occupation, and would probably always favor occupation by a wealthier country with an advanced technology. A similar experience typified the Mongol occupation back in the days of Kublai Khan. At best Rhee has to be judged as a man of highly questionable connections when it comes to the Japanese. At worst, he had beenpart of the Japanese puppet cabal.
The nationalists were wise to jump ship although they were not wise to throw in their lot with Kim Il Sung. One would imagine most of them were disposed of by 1951 during the war.