It is a lack of a PIN issue.

I flew Transavia a few weeks ago and was told that American cards did not work. I tried using my Uber card (issued by Barclays in the US), and it worked - after I entered my PIN. Card issued by Barclays in the US are configured to allow use of a PIN if the terminal requires a PIN. If the terminal does not require a PIN (as in most restaurants in Europe), then the card works as chip and signature.

I have no idea why all US card issuers don't do what Barclays does.

Also, quite likely that Android/Apple Pay would work.