The web link IS THE ONLY way to apply now. The info from the ParisMouth link above is no longer true. Pharmacies have been told to stop proving pass and the email addresses aren’t valid anymore. The web link is easy though and seems to be working for many people. It’s taking 2-12 days. Here is the link and some useful instructions. The link is at the end.
OFFICIAL INSTRUCTIONS FOR AMERICANS to obtain a "pass sanitaire".
Tips: If your screen is acting funny, change browsers. EDGE seems to have problems; GoogleChrome works well.
IF YOU ARE TRAVELING WITH OTHERS, each person must create their own request using their own email. (Children < 12 do not need a pass.) DO NOT use one email to obtain requests for several people.
1) "Residence Abroad" + "Country of Residence Abroad" is your US address. Country = ETATS-UNIS.
2) "Date of Arrival" in France should match the date that shows on your itinerary. It may not be same same as your flight date!
3) "A Copy of your Ticket": get an itinerary or screen print that also shows your name (as well as your flight info)
4) If you have no return ticket, explain that in the freeform text box, and include a pic of your visa or Carte de Séjour. If you click on the MESSAGES tab, you'll see you can attach a doc there.
5) When supplying documents, a scanned image is far more legible than a crummy phone shot. It's a question of respect. Upside-down or sideways images, poorly lit fuzzy images will not earn you brownie points and yes, may get passed over. Do the sure thing and send SCANNED IMAGES only.
6) If all else fails, you can INVITE a 3rd party to see (and modify) your request. Sometimes it takes someone already familiar with French bureaucracy to help.
www.demarches-simplifiees.fr