I flew to Paris from Pittsburgh via Atlanta on March 18. I was unable to upload anything to Verifly before I left. I didn’t try very hard because I knew other people had problems with it.
At the Pittsburgh airport, the Delta rep asked me for my passport. After poking around on her screen for a while, she asked if I had filled out any form. I said I didn’t think one was necessary. (I learned this from Kim on this forum.) She never asked me for my vaccine card. I was not asked for anything in Atlanta besides my passport and boarding pass. While on the plane, they passed out a passenger locator form and collected it before we landed. At immigration in Paris, they only asked for my passport. That was my experience.