This is a great question, and I went back to the rules for my own edification:
“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. While not at war with Germany or Italy, the United States may end the movement of its sea units on the Europe map only in sea zones that are adjacent to U.S. territories, with one exception: U.S. warships (not transports) may also conduct long-range patrols into sea zone 102”.
You can glean the answer from the wording. In Asia, no units can be moved into China. The restriction specifies that it is “all” units. However, for both sea zone 102 and the need to be adjacent to US territories, the restriction clearly only affects “sea units”. As there is no specified rule limiting aircraft in sea zone 102, the carriers can remain loaded as per GHG’s “UK Calling” strategy.
Please also remember that no US units can land on other neutral (or soon to be Allied) territory:
“The United States: The United States begins the game neutral, and as such isn’t initially part of the Allies. Being at war with no one and having a strict isolationist policy, the United States has especially tight restrictions. It may not move land or air units into neutral territories. It may not move units into territories or onto ships belonging to another power or use another power’s naval bases, nor may another power move land or air units into its territories or onto its ships or use its naval bases”.
This doesn’t impede aircraft from being in 102, however.