You can create a specific landing page targeted to those countries on your website and use Google Webmaster Tools to target that specific page to the specific country.
Then the same work you would do for link building on your website, you do it on that page.
So if you were to optimize for Canada for example, do this.
1. Create a www. XXXXXXX .com /ca/ (make sure your on-site keywords have the proper keywords in there, make a keyword research)
2. Target that page to Canada in Webmaster Tools.
3. Link build to www. xxxxx. com /ca/ with keywords such as
– online casino canada
– canadian online casino
– this list will depend on your keyword research and what you are targeting.
Make sure you link on TOP of your page to your specific country page so your link juice travels to that page as one of the first things. The weight of your current home page + the new links targeted to that specific page should do the trick 
Hope this helped.