Interesting - my experiences are quite different. I can order some stuff from Amazon.com (US) from Canada, but many things aren't available. I can't use Amazon Prime (they won't even let me sign up without a US address), and I can't order books for my Amazon Kindle purchased in Dubai (it needs a US address as well).
With Google, however, nearly everything works. I've been using Google Music for some time now, although it isn't officially available in Canada. Same with Google Voice. All I had to do was sign up for both with a VPN for the first use, after which I can access it anywhere through the respective apps in any country with no hassles.