Hello 'ym1813',
As scifan says, you will have to find some other sellers. Some sellers ship only to certain countries, or within their own country. They can set up autoblocks from bidders outside their "ship to" zone. Your ebay ID is registered in Canada, and so you are blocked.
A seller cannot ship to an address other than your registered paypal address (not without losing that seller protection) and you cannot add a foreign address to a Canadian paypal account. You may find sellers willing to ship to another address if you ask, but most will not. Adding alternate addresses to your ebay makes no difference, - sellers are leary of being asked to forego what little protection they have.
When you attempt to contact a seller and get that "unavailable" message, -- that is ebay's idea of a polite refusal. Poorly chosen words, in my view, because it implies you could try again later. What it really means is that the seller has not only blocked bids from your country but blocked questions as well. It means the seller is indeed aware that other countries exist but has chosen not to do business with them. You will have to find another seller.
Happy hunting. 🙂