> I've actually been quite successful in utilizing my Amex card across roughly two dozen countries in Europe and Asia, so this doesn't really match my experience. I haven't specifically tried to use it for a taxi in Paris, however. I do keep a Visa in my wallet in case I need it, but my bigger issue has been places that don't take cards at all, and having to carry cash. Cash only locations are basically nonexistent in the US - even the smallest hole in the wall type places and random food stalls in gas stations tend to allow for cards ever since Square became popular.

I've never used it in Asia, but for example the main Taxi companies like G7: https://www.g7.fr/en/paris-taxi-fares do accept credit cards but are very difficult about amex. When you wait at Charles de Gaulle airport there's some bouncer in the taxi queue who will ask specifically what card you have and if you have Amex then they have to haggle with the queue of waiting taxi drivers for one to accept it. And often when you do get to your destination the machine is suddenly 'broken'.

One of the taxi drivers told me that amex charges them a lot more than the others.

In Romania you'd be hard-pressed to find a taxi that accepts cards at all and if you show them an Amex they will laugh in your face (though taxi drivers aren't very nice people there generally speaking, two of my colleagues even got literally robbed).

The same with other minor expenses. Like rail tickets, food in a 7/11 style shop etc... The big hospitality outlets like upmarket restaurants and hotels do generally accept it. But my work requires me to pay all my travel expenses with amex and I get a lot of bitching from them if I don't. But especially in Eastern Europe I just don't get anywhere with it.