It's very interesting to hear that.
When I first started traveling to Europe, having an American Express card (or even better, AmEx travelers checks) was the best way for an American to pay for things. It's even written into some classic books and movies.
My how things have changed.
I would guess 90% of Europeans have never even seen one of these cards, unless they work in international hotels or tourist places.
And there is a lower % for normal/popular cards (Visa/Mastercard) and higher (even 4%) for Amex, so most stores just ignore it and remove the Amex symbol from their terminal.
And yet, my company provides Amex corporate card for bussiness travel, but we usually go to US, so Amex is more accepted there.
That was one of the deciding factors when I was planning on getting a second credit card (so I'd have a backup while travelling).
I knew here in Australia they are not widely accepted, with only major retailers accepting it typically, but I thought that this was just Australia being backwards.
After spending the first two or three weeks trying to pay for things with it, I gave up except on checking into a new hotel.