Cross-border insurance is a problem. Insurance sold at the U. S. post offices stops at the Canadian border. One parcel shipped insured from Texas was tracked to the border, but couldn't be tracked into Canada. It never arrived. The item was insured for selling price, $300. The shipper was good enough to refund half the price. Expensive items should be shipped by courier only (expensive) since they have their own insurance.
Registered mail is tracked across the border, I use it for small items such as collectable postage stamps. I buy occasionally from UK dealers, the cost to them is about $9; the cost from Canada is $11.00. Registered mail is almost never lost or damaged, but if the item is really expensive, get private insurance to cover.

U. S. banks are barred from dealing in foreign currencies and this causes further difficulties. Foreign money they receive in checks or cash is sent to a Federal Reserve Bank for conversion, with a fee attached.
Many Ebay sellers are private and are not prepared to take plastic. I send U. S. international money orders for sterling to the UK from Canada, but I don't know if this is possible from the States (Canada does permit banks to trade in foreign currencies, only a small number of Federal Reserve banks in the States are allowed to do so).

Rather than blame American Ebay sellers for refusing the headaches of overseas shipment, find out the regulations and rules before you rant about their practices. After all, it is the right of the seller to set their own rules.

Many sellers and buyers refuse to use a third party expense like Paypal; I am one of them. Moreover, some banks here refuse to transfer funds through that type of company. At my bank I would have had to transfer funds to another account in order to deal with them.