@barney:
… The French could amphib on the turn they load.
No, sorry, this part is not correct.
@rulebook:
Transporting Multinational Forces: Transports
belonging to a friendly power can load and offload your
land units, as long as both powers are at war. This is a
three-step process:
1. You load your land units aboard the friendly
transport on your turn.
2. The transport’s controller moves it (or not) on
that player’s turn.
3. You offload your land units on your next turn.
So the French Inf has to wait one turn aboard the US Transport before it can offload.