I think this is a smart idea and it could be a terrific CF community initiative for helping Australian users. All needed for this would be a trusted member of this community forum, living in the USA. This is how it could work:
More info about Steam gifts:
- Trusted US member creates a "CivFanatics Civ5-" Paypal account and publishes the "CivFanatics Civ5-" Paypal address in this forum
- AUS inhabitant sends payment for the desired US Civ5 version combined with his/her Steam username to CivFanatics" Paypal address/account
- After receiving the Paypal money, US member purchases Steam version and gifts it to AUS inhabitant.
https://support.steampowered.com/kb_article.php?ref=6262-QXCN-0755
As long as everyone keeps using the word 'gift', it should be completely legit too.