Is VISA and MasterCard as internationally accepted as they both claim?

In Japan last week, neither of these cards were what I would call widely accepted. Cash was still the only usable currency.

In Denmark today, none of my three cards (two VISA, one MasterCard, from three different banks in two different countries) worked at the industrial design museum; an institution that presumably entertained the odd international traveller. And one of the VISA cards did not work at Copenhagen airport when I flew in last week.

My faith in cards have been shaken somewhat. Need to stock up on cash for fish soup…