Fun fact: the “Amazon Associates” program actually has a different program for a variety of different countries, meaning yes, Amazon.COM has a different program than Amazon.CA, and Amazon.CO.UK, and Amazon.FR, etc. etc. If you want to, you can sign up for all of them without being residents of these countries. What’s important is where your readers are from.
You should also make sure you aren't competing with your own affiliates for eyeballs. Any marketing channels you're using, such as search engines, content sites or e-mail lists, should be off limits to your affiliates. Put marketing restrictions into your affiliate agreement and notify partners immediately. It's your program--you set the rules. Or, if you prefer, you can let your affiliates run the majority of your internet marketing.