Someone on the Rick Steves forum posted this link to the French government on how Americans can get their certificate needed as of yesterday to go into restaurants, museums, public transport, etc. NOTE: Right now they only want people to use the link IF they will be arriving on or before August 15th. It requires downloading a form, filling it out then making electronic copies of it, your passport, CDC card and ticket to email to a specific cite. Even if it's too soon to submit, I know I'll be starting the process this week to have it all ready to go for my husband and I.
https://www.diplomatie.gouv.fr/en/coming-to-france/coronavirus-advice-for-foreign-nationals-in-france/coronavirus-statements/article/applying-for-a-covid-certificate-if-you-were-vaccinated-abroad-procedure-for