What difference does it make, the warranty is not transferable. If I were buying new its an issue as Nikon Canada (Which I live 45 mins from) will only do warranty service on Canadian models.
Used, you are taking your chances regardless of what country the lens was originally intended for. Nikon here will work on any Nikon product for a fee so it's not like you can't have it serviced, just not under warranty if its bought on the second hand market.
p.s. the first reply was dead on as well re: the useless warranty card. I have never filled one in and I have never been asked for it. Nikon has always only asked me for the original bill of sale for any warranty work I have had them do.