Amex Plat did not charge foreign fee, but exchange rate is 1% less favorable according xe.com
Chase Sapphire Reserve also no fees, exchange rate is 0.3% different from xe.com
Don't get me wrong, there are tons of options for cheap or downright free foreign exchange transactions (such as Revolut, N26, Fortuneo, BoursoBank just in France). It's Amex in particular that are borderline scamming their French customers on foreign transactions.
Funnily I've gotten notified a couple of times by Amex, as per ECB regulations, that the course they've used is significantly worse than the official one.
Even in the US, this is not true. The Blue Cash Preferred and Everyday Preferred cards have foreign transaction fees, as does the Business Green card.
Practically all non-US-issued Amex cards have foreign transaction fees as well. The US card market seems to be very competitive on that front.