You can list on .ca so that you can use the shipping options available in Canada. It is a good idea to do that if you are shipping heavier items as then you can use calculated shipping rather than a flat rate.
Or
If you list on .com you can't use calculated shipping but will need to put in amount for the whole country. For shipping to the U.S. use a flat rate under
"standard shipping from outside U.S." You can also use economy and expedited shipping from outside U.S. Each category will show U.S. buyers a different arrival time. I use standard as it will show them an arrival of 5-10 business days.
To show your flat rates within Canada and to other countries when listing on .com, use "standard international shipping"
I hope that helps (and makes sense) 🙂