[WooCommerce 3.0+] Custom sorting for checkout page country dropdown

wc-sort-checkout-countries-custom.php

// disable woocommerce sorting
add_filter( 'woocommerce_sort_countries', '__return_false' );

add_filter( 'woocommerce_countries',  'wc_custom_countries_order', 10, 1 );
function wc_custom_countries_order( $countries ) {
  // replace with iso code of the country (example: US or GB)
  unset($countries['country_1_iso_code']);
  unset($countries['country_2_iso_code']);
  unset($countries['country_3_iso_code']);
  // replace with iso code of country AND country name (example: US | United States or GB | United Kingdom (UK)
  $countries = ['country_1_iso' => 'country_1_name'] + ['country_2_iso' => 'country_2_name'] + ['country_3_iso' => 'country_3_name'] + $countries;
  
  return $countries;
}

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