Check the user's country and show them as a warning using SweetAlert2. Warning was shown on Checkout page if the country is other than Germany in this example.

functions.php

<?php
function get_user_geo_country(){
    if(is_checkout()) {
        $geo      = new WC_Geolocation(); // Get WC_Geolocation instance object
        $user_ip  = $geo->get_ip_address(); // Get user IP
        $user_geo = $geo->geolocate_ip( $user_ip ); // Get geolocated user data.
        $country  = $user_geo['country']; // Get the country code
        if($country != 'DE') {
        ?>
            <script src="https://cdn.jsdelivr.net/npm/sweetalert2@9"></script>
            <script>
                Swal.fire({
                   title: 'Achtung!',
                   html: 'Ihr Land: <?php echo WC()->countries->countries[ $country ] ?>!<br>Wir versenden nur innerhalb Deutschland.',
                   icon: 'warning',
                })
            </script>
        <?php
        }
    }
}

add_action('wp_footer', 'get_user_geo_country');