You need to use the HREFLANG markup.
If you Google my site on Google.com, it displays and takes you to highonseo.com, if you search Google.com.au, it takes you to HighonSEO.com.au Make sense?
Add these tags to your pages in the head area. This should take about a week to "kick in" and far less time if you update regularly and Google comes and crawls you sooner.
<link rel="alternate" <span class="il">hreflang="en-Us" href="http://www.example.com/US" /></link rel="alternate" <span>
<link rel="alternate" <span class="il">hreflang</link rel="alternate" <span>="en-UK" href="http://www.example.com/UK" />
<link rel="alternate" <span class="il">hreflang</link rel="alternate" <span>="en-AU" href="http://www.example.com/australia" />
<link rel="alternate" <span class="il">hreflang</link rel="alternate" <span>="en-CA" href="http://www.example.com/canada" />
More on HREFLANG:
http://support.google.com/webmasters/bin/answer.py?hl=en&answer=189077
I love talking about SEO and I type fast so it helps get those thoughts out. Appreciate the comment.