Yesterday I had this discussion with a former employer. Sometimes a company, say a hard drive maker, will produce a hard drive for use in the US. The same hard drive (by name only) could be available from Canada as well, but the serial number would be different. The difference, besides the s/n, is the fact that the Canadian one uses inferior parts.
When a customer recently came in to get a hard drive replaced by warranty, we ended up calling the manufacturer and they simply stated that since it was for use in a different country, there was absolutely no warranty here from the US. The way the manufacturer notes which drive used good parts was only by the serial number.
Besides that, though, is the fact that our sue-happy consumers ensure that the manufacturers use better parts so we don't have to return them when defective as often.
Buyer beware.