@flyingbadger said in Loading units onto allied transports in the same round that the ally unloaded them:
… even though the US transports have already loaded/unloaded on that round?
During US turn rules concerning movement and loading/unloading transports apply to the US. So restrictions apply to US turn, see rulebook’s Transport rules. They do not apply to the entire round. In your scenario it is France’s / UK’s turn.
This is why the rules that you quoted say “You (as French or as UK) move land units aboard”, and “You (as French or as UK) offload your units.”. The US transport has no active role here, as it is not US’ turn.