EU used to be very popular with chip & pin (more secure) payments instead of U.S.''''s chip & signature but EU has since learned to accept U.S. payments so mostly it is no longer an issue using U.S. CC in EU.

Just watch out for foreign transaction fees and DCC (Direct currency conversion， which gives you crappy exchange rate). Always use a CC without foreign transaction fees and always insist upon paying local currency (instead of USD). That will let your CC take care of the exchange rate instead of a local 3rd party. Of course if you have a chip and pin US CC then bring it alongand you should be all set without needing cash. Mind you chip & pin US CCs are rare. Out of many CCs I have, only Barclay''s American Airline CC has chip and pin.