The short answer is yes, though there are certain online retailers which have payment processing systems that reject foreign credit cards. Why, I'm not sure -- this was just my experience when I lived in the UK. I don't know if Argos is one of those -- I do recall that in the stores you could only pay with a chip and pin card (not a swipey only card). You can always call to check. However, also be aware that unless the American buyers are paying with a Capital One credit card, they will get hit with a foreign transaction fee, which typically ranges anywhere from 1.5-3%.