Can us and uk share sea zone before US is at war?

Yes, as long as the sea zone doesn’t border europe or africa

Keep in mind that does not mean that if Italy or Germany attacks that sea zone that they are attacking the US ships unless they specifically state so. In other words you can protect your British ships with an invulnerability field from US ships. haha

can the US move into seazones bordering australia before “at war”?

@katfishkris:

can the US move into seazones bordering australia before “at war”?

Yes

Remember that while they can move into these sea zones it does not mean that they may land ground units. They must wait to land ground units until they are at war.

@beavis6:

ok, so part 2 of my question, if the US moves Naval units into a sea zone shared with UK naval units AND the US is not at war yet, does this prevent Japan from attacking the UK fleet there UNLESS Japan declares War against US?

No, Japan can ignore US fleet

@beavis6:

Another follow up to my questions because I’m still debating this point with a friend:

If USA is not at war
if UK is at war
if USA naval units share a sea zone with UK units and Japan attacks

Then are these points correct:
1. Japan can attack the sea zone
2. UK and US naval units defend together
3. This is not a declaration of war by Japan against USA

or are these points correct:
1. Japan can attack the sea zone
2. UK naval units defend
3. ignore USA naval units in the battle.

Any powers may share a SZ with any power they are not at war with. If US, ANZAC and UK share the same SZ Japan (who is not at war with any of them) can declare war on US, only and ignore UK and ANZAC ships. It could also choose to declare war on UK and ANZAC ignoring the US letting the US declare war next turn. It could also attack all of them.

@beavis6:

Another follow up to my questions because I’m still debating this point with a friend:

If USA is not at war
if UK is at war
if USA naval units share a sea zone with UK units and Japan attacks

Then are these points correct:
1. Japan can attack the sea zone
2. UK and US naval units defend together
3. This is not a declaration of war by Japan against USA

or are these points correct:
1. Japan can attack the sea zone
2. UK naval units defend
3. ignore USA naval units in the battle.

Red part of edited quote above is correct to the best of my knowledge and experience.

See page 15 AAEurope 1940 rulebook-blue sidebox section, third paragraph beginning with “Combat:” second sentence: “If a power at war attacks a sea zone containing units belonging to both a power with which it’s already at war and a power with which it’s not at war, the latter power’s units are ignored.”

Note: This is not an official answer, just helping out.