Ironic, in that American Express (AMEX) traveler's cheques used to be (before credit cards were common) a nearly universal way for American tourists to carry cash when traveling anywhere in Europe, you could always exchange them for the local currency, and they would be replaced if lost/stolen.
Are you trying to use it in tourist areas or not? It makes a big difference. My employer a few years ago was bought by a US company who switched the corporate cards from Visa to Amex, and after that, every business trip to Ireland from the US offices had someone needing to claim reimbursement for paying without the company approved card as the Amex got rejected at least once on each trip. We used to joke that it was an attempt to reduce the cost of expenses by annoying people with the paperwork when the Amex was inevitably declined.
I live in Australia when I first signed up for a credit card through my bank they issued me with both a Mastercard and an American Express card linked to the same credit account. It seemed to me they really wanted to push Amex as they offered higher reward points etc for using it, the problem was almost nowhere accepted Amex whilst Mastercard "just worked" everywhere.
Eventually my bank cancelled the Amex card and they no longer offer American Express. I never really noticed because I hadn't used it for years at that point.
I've travel in Europe a bunch (CEE, Scandinavia, and UK) for work and pleasure and Amex has always worked for me. I can only think of a handful of times where I had to revert to my Visa instead.
not so in the UK, especially London. strong presence. they’re accepted even at local shops where they dropped their fees in order to encourage adoption.