Hmm, I just double-checked and I don't get that. I'm in Canada. Have two addresses registered, both Canadian. For example, [1] is appears to be available, and also claims to have free shipping (as do many items listed on amazon.com eve though the free shipping is US only). When I add it to my cart, proceed to checkout, and choose an address though, it lets me know about the "slight problem" with my order... the fact that I can't get it.
Maybe it's only Amazon Fulfillment items that do this?
[1]: http://www.amazon.com/gp/product/B009ENG6TI/ref=ox_sc_sfl_ti...