Japan not attacking round 1 also has a similar strategy. You can focus on china for a turn and if you plan on a sea-lion attack with germany and the german turn went well you might want to prevent the US from doing anything for a few rounds.
With Sea-lion as a viable alternative and Japan in striking position but not yet at war anzac and the UK have to be carefull while the US has to decide how to split its money if they spend all on europe to maby counter sea-lion or liberate fast then japan can really mess around.