Moving next to captured Japanese islands

[SuperbattleshipYamato]

If Japan is at war with the UK and France but not the US, and has captured Borneo, can the US move submarines to the sea zone next to it?

[AndrewAAGamer]

Per the Pacific 1940 2nd Edition Rulebook (Page 37)

(Bold added by me)
In addition to the normal restrictions (see “Powers Not at War with One Another,” page 15), while it’s not at war with Japan, the United States may not move any units into or through China or end the movement of its sea units in sea zones that are adjacent to Japan-controlled territories.

Since, in your described scenario, the USA is still Neutral and Borneo is controlled by Japan the US would not be able to move any US sea units into the sea zone surrounding Borneo.

[SuperbattleshipYamato]

@andrewaagamer

Thank you!