Need to rank both in the US and AUS

Selected answers from the Dumb SEO Questions Facebook & G+ community.

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  Jeff Oxford: your best bet would be having separate .au domain. The advantage here is that country specific domains tend to rank better in their country and often times users of other countries prefer websites with the ccTLD of their country.
  
  But the one downside is that you`ll need to double your link building efforts since you would be doing link building for 2 websites instead of 1. So you really can`t go wrong with a separate domain or subsection...just not a subdomain.
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  Glenn Cooper: Such bad advice... doubling efforts all over the place
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  John Smith: Use com, but you can make /au.....
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  Steve Toth: Usually put the language in there .com/en-au/
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  Ammon Johns: Domains are cheap, but whether you need an AU domain really depends on whether customers prefer one when selecting which site in a list of results to look at.
  
  However, much more important is that different regions, cultures, and economies, really need their own unique sales pitch if you really want to maximize the conversion rates. So wherever your AU traffic is landing that differs from your US traffic, the content ought to be tailored to the specific of the difference in market, pricing, taxes, and most importantly mindset of the customer.
  
  If all that changes is the pricing you are missing a way, way bigger point than the domain issue.
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  Michael Stricker: Ammon Johns yup... and currency... and shipping. Which is one big reason why a .au might be worth the extra effort, if that regionalized TLD is what shoppers are looking for, regardless of search.
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  Loren Baker: If I lived in Australia, I`d probably think twice about clicking on or purchasing from a .com vs. a .com.au