If you are traveling out of the country, be sure to call your credit card company and have them place a note on your account regarding your trip. If their computers suddently see a bunch of activity internationally it is likely to trigger the fraud alerts. Letting them know ahead of time won’t guarantee that it won’t get cut off, but it can help. In my experience American Express is less likely be cut off than Visa or Mastercard.
In my limited european mostly experience, I have noticed that it is the specific location that matters most not simply the country. Are you using the card in a reputable hotel, store etc? or some other dingy place?
I.
One of the places I had trouble using anything but Amex was in an Office Depot in Mexico. My Visa’s wouldn’t work, but American Express went through just fine.