Weird is right! There's no such thing as an "international credit card". Where in the world would you get such a card? All Visa, Mastercard, and American Express are international regardless of where you got them. They're all on the same international network.
I've used my Amex and Mastercard all over the world. The only problem I've had is when stores in the country I am in don't accept my Amex. Other than that, no problems at all, including ordering internationally.
Patagonia has localizations with their merchandise, though. Living in Japan I can't order from Patagonia in the States. I can only order from Patagonia, Japan. Really sucks.