What SEO strategy do you use to sell products in multiple countries?

Hi All I have an affiliate web site that sells products in multiple countries. I currently structure the site as such: http://www.mysite.com/product1 for the US version of the product http://www.mysite.com/ca/product1 for the Canadian version of the product http://www.mysite.com/uk/product1 for the United Kingdom version of the product The "product1" page is identical for each country except for the prices. My problem is that a Google spider will see the pages in other countries and mark them as duplicate, as I have a country link at the top of each page. Thus I mark every country link (including US) as "nofollow", thus hopefully the duplicate content isn't picked up. My question is: Is this URL structured approach a good SEO strategy for dealing with products in multiple countries? Or should I be using country specific domain names and redirecting to them (but surely I can't use "nofollow" then and Google will mark the content as duplicate). What experiences do you have with this problem and what issues can you envisage will occur? Thanks.