Hey Austachian, Another Aussie expat here living in the US.
I elected not to have a 401k, because I'm not planning on staying here long term - I had a brief discussion on the phone with a rep at the firm our company runs the 401k through, and elected not to do it. Keen to see what others suggest though.
I'd be curious, while we're here - to know what you have done regarding Aussie and US based assets - and what you're planning to do in future.
I have some VAS shares on the ASX in Australia. Plus our emergency cash fund is sitting in a 'high' interest savings account in Australia. Most of our money is currently in USD here in the US, and I'm currently debating whether to send money back to Australia, or leave it here. I've been waiting for the AUD to drop below 70 cents before I send any more back.
I was able to open an investment account here with Vanguard - other brokers turned me down because I don't have permanent residency. I'm now wondering if I keep USD invested here locally, as a way to hedge against an Australian market crash. The only issue then is that it makes my tax returns more complex, and I will need to do a tax return for AUS and the US every 6 months, so long as I keep assets in both countries.