The problem was resolved after nearly 2 hours with Apple Chat support. TL;DR: Changing billing address in Wallet does not update the backend -- that is why a Card may show correct billing address in Wallet but not at appleid.com. To change billing address you need to delete the card associated with the incorrect billing address and add it back with the desired billing address.
Here are the steps that worked for me:
(1) Delete my Apple Card and Bank card from Settings > Wallet & Apple Pay,
(2) from Settings > [Apple ID, iCloud, Media & Purchases] at the top of Settings perform the following additional steps:
(3) Select Payment & Shipping,
(4) set default payment to Apple Cash (tap Edit, drag Apple Cash to top) -- this step *may* be optional if you don't have Apple Cash
(5) Delete Apple Card and Bank Card,
(6) Add back Bank card -- which allows setting the appropriate billing address,
(7) Add back Apple Card.
(8) Set Default Card (tap Edit, drag default card to top)
(9) Go back to Settings > Wallet & Apple Pay and add Bank Card and Apple Card to Wallet
(10) Go to appleid.com and confirm appropriate billing address in Payment & Shipping
@Eric Root: I was able to edit the billing address from AppleID.com until I changed the default payment option to Apple Card -- so it appears that editing billing address is permitted with Bank card as default payment option; restricted when Apple Card is the default.
I hope this helps.