I recently attempted to file a return protection claim with my Sapphire Reserve for a display cable that turned out to be faulty. I tried the Visa Infinite site, but Visa as an organization doesn't recognize the United States as a Visa Infinite country yet so I couldn't find anything relevant there.
Then I recalled eclaimsline, which was the site I used a while ago when I had the Sapphire Preferred. It asked for my first/last name and credit card number, and then did not show me the option to file a 'return protection' claim -- just purchase and travel protection.
After that, I went on Chase's website and dug through their documentation and eventually found cardbenefitservices.com, where I was prompted to create a new account and then verify my card number again. Upon filing a claim, I was asked to upload my purchase receipt and credit card statement proving the charge had hit my account. I waited one week and received an email in my spam folder that asked me to mail the item at my own expense to Visa before my claim could finish processing -- mind you, this is for a $20 display cable.
My experience with Amex would have been a three-step online form containing a very small number of fields followed by an immediate credit within 48 hours.