Yes, it is possible to list on eBay Canada and have the shipping reflect US shipping options. When you are creating a listing and select eBay Canada as the site to list on, you will need to go to the Shipping Tools section of the lister to state that it is being shipped from the US.
In the top part of this section, you can choose the location that the item is in (or will be shipped from.) Where it says Country, enter the US (as well as the Zip code or city/state), and then the USPS shipping options will be available.
I hope that answers your questions~if not, don't hesitate to ask