No, you cannot obtain a U.S. credit card unless you are a U.S. resident and have a physical address and sometimes a Social Security number. P.O. Boxes are not usually acceptable mailing addresses for obtaining a credit card. There are a couple of ways to obtain a card when you are a non-U.S. resident. The first is to call different U.S. banks and ask if they will issue a card to you. Another one is to hire a lawyer who specializes in this, but this is rather expensive way.