I have had endless issues abroad with my credit card companies in the U.S. If I don’t let them know beforehand that I’m traveling, they always end up putting a block on my card, thinking it’s transactional fraud. While I appreciate the high level of security, it’s a huge nuisance and headache when I have to call to verify the transactions and wait a few days until they send me a new card. So the easiest way to prevent that headache, not to mention embarrassment is to let them know, so they can put a note in your file.