Yeah, I think digital literacy courses cover things like that, and they should.

But mailing addresses are actually extremely complicated and most people probably don't understand the full scope even of US mailing addresses. The spec is 226 pages.[0]

[0]: https://pe.usps.com/cpim/ftp/pubs/Pub28/pub28.pdf

If you've ever had an address with any complexities beyond what is taught in elementary school (number, street, city, state, zip), you'll probably experience issues with getting others to correctly address your mail. The biggest reason this isn't a problem is because the postal service takes significant effort to deliver misaddressed mail.