http://upload.wikimedia.org/wikipedia/commons/f/fa/Operation_Downfall_-_Map.jpg
Reviewing the map above for Operation Coronet, I see 1st Army being the entire organization of what is currently 10th Army on Okinawa. Only the 1st Army HQ has been substituted. Other than the armored corps in floating reserve, I see no units from the ETO.
Am I missing something, or is this map inaccurate?
I think the map is accurate. It's a copy of the map in the Army's West Point Atlas for WWII, Pacific Theater. I found the same information in another Army publication describing MacArthur's WWII campaigns.
I just spot checked 2nd Inf. Div.'s Wiki and in accordance with the Times story by VJ Day they were in the U.S. training for deployment to the Pacific.
Which leads to the question, for what operation were they training? Two possibilities come to mind. They may be anticipating subsequent reinforcement or replacement of the initial Coronet units. Or they may be slated for future operations if a successful Coronet does not cause the Japanese to surrender.
Incidentally, whenever I think about Operation Coronet, I inevitably also think about Coronet Films. I couldn't begin to tell you how many of their movies I saw in the classroom as a schoolboy.