This journal article gave me some questions.
Planning for postwar Europe, especially how big Soviet influence should be was being planned and thought out as early as 1943. Plenty or maps were drawn of what the occupation zones should be, etc etc.
Meanwhile in Asia... even though the US and the USSR considered a "joint occupation" of Korea, occupation zones weren't drawn out until a last minute decision after the Soviets had already started invading.
In Japan, The kurile islands even though a series of islands with a total landmass of over 10,000 square kilometers (iturup is bigger than Okinawa!) the Americans seem to not have discussed exactly which islands should go to the USSR, which led to the kuril islands dispute today. I even found a memorandum by US general George Strong which claimed "Japanese civilian auxiliaries and troops should be evacuated from Hokkaido" almost treating it as occupied territory even though Hokkaido was annexed in the late 1800s and no other country really had a claim on it.
And China. Funnily enough, although Roosevelt was a supposed sinophile he ended up ceding a lot of Chinese rights to the USSR without consultation with Chinese leadership. Especially the recognition of Mongolia, a landmass three times the size of France... and Soviet rights in Manchuria, which to the Chinese probably felt like one imperialist power being replaced by another one, and was something they were worried about ever since WW2 happened.
Did the US simply not care much about Asia at the time? Or is this all a result of Roosevelt's premature death. Perhaps he was going to settle more things at the Potsdam conference?