OTOH, the US was surprised that the Soviets accepted the 38th parallel. The Soviets seemed to be in a much stronger position to occupy Korea; the nearest US troops were far away, in Okinawa. See my post at
https://groups.google.com/d/msg/soc.history.what-if/9d1jVAIdvf0/F8pxmNk3jG4J where I point out that Admiral Gardner actually proposed the 39th parallel, and that this was rejected because the Soviets were unlikely to accept it. In any event, the US was very anxious to prevent the Soviets from occupying all of Korea, and to be sure that Seoul and Inchon were included in the American zone. (Inchon was important not only because it was a port but because many American prisoners of war were being held there).
However, Michael Sandusky apparently argued in *America's Parallel* (I have not read the book and am quoting R. A. Harris' post on it) that "given the positions and strengths of all allied forces as of 15 August, and their logistical capacities, the Americans could have beaten the Soviets to northern Korea up to the 40th or 41st parallel in Korea and the Liaotung peninsula if they were inclined to do so and optimized their deployments for such a purpose. He asserts that the rate and inevitability of Soviet advance was overestimated at the time and in years since..."
https://www.alternatehistory.com/fo...had-different-korea-maps.301686/#post-8860722