Can't save data for Address field
The problem here was due to Drupal failing silently (or obfuscating the error - maybe because I was running this in cron) but it was due to the address not having all of the required fields set to the correct values for the country in question - mainly using the actual country name instead of the country code.

Once the country code was swapped in it worked. I switched the country around to the country code like this:

function MY_MODULE_get_country_code($country) {
  $countries = MY_MODULE_country_list();
  $flipped_countries = array_flip($countries);
  $country_code = $flipped_countries[$country];
  return $country_code;
}

function MY_MODULE_country_list() {
  $countries = \Drupal\Core\Locale\CountryManager::getStandardList();
  foreach ($countries as $key =&gt; $value) {
    $countries[$key] = $value-&gt;__toString();
  }
  return $countries;
}


It worked correctly.