If you offer your items for sale on .com with international shipping, it will not show on .ca. If you offer it on .ca, it will show the “ships from the US” disclaimer. If you want to offer on .ca without the disclaimer, the items need to ship from a Canadian address.
You may also want to look into the program where FBA sends your stuff from the US to Canadian warehouses to sell on .ca. I can’t remember the name of the program right now. Remote Fulfillment maybe?