Importing countries in taxonomy hierarchically per region/continent

import-taxonomy-terms.php

<?php

/**
 *  Intended to run via WP-CLI using 'wp eval-file import-taxonomy-terms.php' command
 */

// Ensure WordPress is loaded
if ( ! defined('WPINC') ) {
    die;
}

function insert_country_terms() {
    $taxonomy = 'country'; // Your custom taxonomy slug
    $countries_hierarchy = array(
			'Africa' => array(
					'Algeria',
					'Angola',
					'Benin',
					'Botswana',
					'Burkina Faso',
					'Burundi',
					'Cabo Verde',
					'Cameroon',
					'Central African Republic',
					'Chad',
					'Comoros',
					'Congo',
					'Djibouti',
					'Egypt',
					'Equatorial Guinea',
					'Eritrea',
					'Eswatini',
					'Ethiopia',
					'Gabon',
					'Gambia',
					'Ghana',
					'Guinea',
					'Guinea-Bissau',
					'Ivory Coast',
					'Kenya',
					'Lesotho',
					'Liberia',
					'Libya',
					'Madagascar',
					'Malawi',
					'Mali',
					'Mauritania',
					'Mauritius',
					'Morocco',
					'Mozambique',
					'Namibia',
					'Niger',
					'Nigeria',
					'Rwanda',
					'Sao Tome and Principe',
					'Senegal',
					'Seychelles',
					'Sierra Leone',
					'Somalia',
					'South Africa',
					'South Sudan',
					'Sudan',
					'Tanzania',
					'Togo',
					'Tunisia',
					'Uganda',
					'Zambia',
					'Zimbabwe'
			),
			'Asia' => array(
					'Afghanistan',
					'Armenia',
					'Azerbaijan',
					'Bahrain',
					'Bangladesh',
					'Bhutan',
					'Brunei',
					'Cambodia',
					'China',
					'Cyprus',
					'Georgia',
					'India',
					'Indonesia',
					'Iran',
					'Iraq',
					'Israel',
					'Japan',
					'Jordan',
					'Kazakhstan',
					'Kuwait',
					'Kyrgyzstan',
					'Laos',
					'Lebanon',
					'Malaysia',
					'Maldives',
					'Mongolia',
					'Myanmar',
					'Nepal',
					'North Korea',
					'Oman',
					'Pakistan',
					'Palestine',
					'Philippines',
					'Qatar',
					'Saudi Arabia',
					'Singapore',
					'South Korea',
					'Sri Lanka',
					'Syria',
					'Taiwan',
					'Tajikistan',
					'Thailand',
					'Timor-Leste',
					'Turkey',
					'Turkmenistan',
					'United Arab Emirates',
					'Uzbekistan',
					'Vietnam',
					'Yemen'
			),
			'Europe' => array(
					'Albania',
					'Andorra',
					'Armenia',
					'Austria',
					'Azerbaijan',
					'Belarus',
					'Belgium',
					'Bosnia and Herzegovina',
					'Bulgaria',
					'Croatia',
					'Cyprus',
					'Czech Republic',
					'Denmark',
					'Estonia',
					'Finland',
					'France',
					'Georgia',
					'Germany',
					'Greece',
					'Hungary',
					'Iceland',
					'Ireland',
					'Italy',
					'Kazakhstan',
					'Kosovo',
					'Latvia',
					'Liechtenstein',
					'Lithuania',
					'Luxembourg',
					'Malta',
					'Moldova',
					'Monaco',
					'Montenegro',
					'Netherlands',
					'North Macedonia',
					'Norway',
					'Poland',
					'Portugal',
					'Romania',
					'Russia',
					'San Marino',
					'Serbia',
					'Slovakia',
					'Slovenia',
					'Spain',
					'Sweden',
					'Switzerland',
					'Turkey',
					'Ukraine',
					'United Kingdom',
					'Vatican City'
			),
			'North America' => array(
					'Antigua and Barbuda',
					'Bahamas',
					'Barbados',
					'Belize',
					'Canada',
					'Costa Rica',
					'Cuba',
					'Dominica',
					'Dominican Republic',
					'El Salvador',
					'Grenada',
					'Guatemala',
					'Haiti',
					'Honduras',
					'Jamaica',
					'Mexico',
					'Nicaragua',
					'Panama',
					'Saint Kitts and Nevis',
					'Saint Lucia',
					'Saint Vincent and the Grenadines',
					'Trinidad and Tobago',
					'United States'
			),
			'Oceania' => array(
					'Australia',
					'Fiji',
					'Kiribati',
					'Marshall Islands',
					'Micronesia',
					'Nauru',
					'New Zealand',
					'Palau',
					'Papua New Guinea',
					'Samoa',
					'Solomon Islands',
					'Tonga',
					'Tuvalu',
					'Vanuatu'
			),
			'South America' => array(
					'Argentina',
					'Bolivia',
					'Brazil',
					'Chile',
					'Colombia',
					'Ecuador',
					'Guyana',
					'Paraguay',
					'Peru',
					'Suriname',
					'Uruguay',
					'Venezuela'
			)
		);	

    foreach ($countries_hierarchy as $region => $countries) {
        // Insert the region term
        if (!term_exists($region, $taxonomy)) {
            $region_term = wp_insert_term($region, $taxonomy);
        } else {
            $region_term = get_term_by('name', $region, $taxonomy);
        }

        if (is_wp_error($region_term)) {
            echo 'Failed to insert region: ' . $region . "\n";
            continue;
        }

        $region_term_id = is_wp_error($region_term) ? $region_term->get_error_data() : $region_term['term_id'];

        // Insert the country terms
        foreach ($countries as $country) {
            if (!term_exists($country, $taxonomy)) {
                wp_insert_term($country, $taxonomy, array('parent' => $region_term_id));
            }
        }
    }

    echo 'Terms have been imported successfully.' . "\n";
}

insert_country_terms();