A credit card is, well, a credit with rates etc. You may pay a part and the rest runs as a credit. You have a specific contact for that. Also a credit card can be issues without a backing bank account. Our cards always (in practical sense) are backed by an account.
This is not how the cards work in the EU. You have delayed debit but no credit (formally - in practice you spend the money of the bank obviously, but you have to pay in full after 30-45 days).
American Express is a system that is used by companies (for various reasons) and this IS a credit card, but people use it for business related reasons and its delivery is triggered by the company.