Seems hard to believe for Syria, since a fair number of Americans travel there. I do know that Iran is totally disconnected from our credit card system, even for making and holding reservations. (I'm too young to know the pre-credit card era, but trying to make reservations without one seems annoying.)

Or maybe a non-Schwab card.
I think if you posted this in the Middle East travel forum you might reach more eyeballs of people who've been to Syria.