function restrict_login_page_by_country_idc() {
    if (strpos($_SERVER['REQUEST_URI'], '/wp-login.php') !== false) {
        if (!country_specific_idc()) {
            wp_redirect('https://yoursite.com/');
            exit;
        }
    }
}
add_action('init', 'restrict_login_page_by_country_idc');

function country_specific_idc() {
    $ip_address = $_SERVER['REMOTE_ADDR'];
    $url = "https://ipapi.co/{$ip_address}/country/";
    $response = wp_remote_get($url);
    if (!is_wp_error($response)) {
        $body = wp_remote_retrieve_body($response);

        if (strtolower(trim($body)) === 'us') {
            return true;
        }
    }
    
    return false;
}