No problem .. package and check rate on Canada Post site for US Expedited . Enter dimensions , weight etc. and send buyer an invoice. Shipping address is in "details" of your payment in PayPal. Do not use" recalculate" when adding shipping to the invoice. Just preview and send.
Either add US to your listings ( big buyer pool) or set your buyer requirements to block. Must do to block countries that you do not wish to ship to..
http://pages.ebay.ca/help/sell/buyer-requirements.html