It's possible, but not particularly easy. Generally, they want to see residency (or at least a part-time address) in the US. Since most Canadians don't have social security numbers (Canadian social insurance numbers are basically useless in the US) Canadians obtaining credit in the US generally needs an Individual Tax Information Number (ITIN) from the IRS, which acts like an SSN for people who can't have one. Amex will consider the fact that somebody is a cardholder in Canada, but it's not automatic that will translate into obtaining a US card. I have a friend who went through it a while back and while he got it done in the end, there were hoops he had to jump though.