Of course, the post office here in Mountain View meets every one of the ADA requirements. Looks as if it was built that way from the beginning, but if it is a retrofit, it is a good one. Not a pretty building, but you could certainly tell it's a post office from a mile away.
I remember being in Whaletown on Quadra Island, BC and found this Canadian post office. It's so very cute, but totally unusable as a PO.
It might not be a post office. It had no one inside, but the door was open. I mailed a few postcards from there and as far as I know they are probably still in the box outside. But I loved the building so much I had to take a picture of it. This was probably 10 years ago while traveling from Victoria to Nanaimo to Tofino and on to Port Hardy where the island ends.
US PO rating - 5