My card doesn't work (and I'm outside the US).
Usually, the issuing bank (the bank that gave you the card) is declining the transaction. This can happen even if the card is valid, and even if it works with other US merchants. Banks evaluate transaction attempts using a complex set of rules, including location and type of business.
You may be able to allow the transaction by contacting your bank and asking them not to block it. Unfortunately, there's nothing that Destroy All Software can do to make a failing transaction go through.
Can you show your keystrokes on-screen?
This is unlikely for two reasons. First, I constantly make tiny mistakes that I immediately correct, making the keystrokes nearly unintelligible when printed out. Second, it would take up screen real estate, which is already limited.