Drawback can be claimed on shipments to Mexico or Canada for certain types of unused and rejected merchandise and still receive a full drawback refund.  Identification of the exported merchandise back to its original importation is required for full recoveries using either a specific or accounting method.  Unused merchandise substitution drawback is not allowed on shipment to either CA or MX.
Manufacturing drawback and unused merchandise that is no longer in the same condition can be filed but these claims require a comparison of duties paid into the US to duties paid into CA or MX and you receive 99% of the lesser of two duties amout.