Clear Billing Country on Checkout Load

functions.php

<?php 
add_filter( 'woocommerce_checkout_get_value', function( $value, $input ) {

    // Run only on the front-end checkout page
    if ( is_admin() || ! is_checkout() || is_wc_endpoint_url() ) {
        return $value;
    }

    // Clear only the billing country on first load
    if ( $input === 'billing_country' ) {

        // If user has not submitted anything yet, force it blank
        if ( empty( $_POST['billing_country'] ) ) {
            return '';
        }
    }

    return $value;
}, 10, 2 );


// Automatically Sync Billing Country if “Same As Shipping” is Checked
add_action( 'woocommerce_checkout_update_order_review', function( $post_data ) {

    parse_str( $post_data, $data );

    // If "same as shipping" is checked
    if ( isset( $data['billing_same_as_shipping'] ) ) {

        if ( isset( $data['shipping_country'] ) ) {
            $_POST['billing_country'] = $data['shipping_country'];
        }
    }
});

?>