I'm sure their system has its faults, but I find shipping to the UK via postal code quite easy.
"A full postcode identifies a group of addresses (typically around ten) or a major delivery point."
https://en.wikipedia.org/wiki/Postcodes_in_the_United_Kingdo...
"A full postcode identifies a group of addresses (typically around ten) or a major delivery point."
The United States can be more granular, as a "full postcode" equivalent in the United States is ZIP+4, which can resolve down to an individual building, mailbox, or person, depending on the characteristics of the location.
Interestingly, there are no polygons for UK postcodes, because UK postcodes don’t represent a geographical area; instead, they represent one or more discrete points.