Just don't travel to Europe, you will struggle with amex here. Almost unknown at any selling point and as per what others post for good reasons.
Depends on the country. Worked fine in Portugal, Italy, Norway and Britain. Less so in France and Germany—they have influential financial centres.
Good coverage in London, UK but not as much as the US
only fancy restaurants in France/Spain
some small biz places in Venice, Italy but probably only because of the Venice Biennale was sponsored by Amex and their sales people did a push.
Europe is a big place.
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.