Amazon doesn't only sell its own stuff, it also markets other merchants' wares and these don't always ship outside the US. I had that problem until I got the Aramex Shop&Ship account with the US address and entered that during checkout as the shipping address. No problems.

Ebay is great but paying for stuff is a hassle as I don't have a US-issued credit credit card. I used to pay sellers through Bidpay but that shut down. I think it's just reopened.