It depends on two things.
Did you specify shipping amounts in the Sel Your Item form for Canada or Worldwide and did you exclude any countries from your shipping preferences (default is you ship to all countries when you choose to ship Worldwide.).
How is yoiur shipping stated in the above form? If you put the Worldwide first (you listed it or chose it forst) the buyer would see only that shipping first and not his own country's.
When searching did you search Worldwide (box on bottom left) when searching? Default is USA only or for me, Canada only, which does, by the way, show USA or Canada (and same to you) Only If the seller has chosen to include shipping amounts for Canada or USA.
I or you can choose Wporldwide searching and see most of what is listed.
I wemt to 3
ebay sites and typed in the serach phrase 'australia kgv' in the main page's search box and got these reslts, showing all items in Stamps, first without choosing any worldwide and then choosing worldwide.
ebay ca = 3,720 . . . 3,945
ebay com = 3.764 . . . 3,945
ebay com au = 689 . . . . 1,481
so we can see each other's but Australia people can only see certain ones. I am not sure why this is.