Snippet to adjust UPS shipping rates based on the destination country and state. WooCommerce UPS Shipping Plugin: https://www.pluginhive.com/product/woocommerce-ups-shipping-plugin-with-print-label/

functions.php

add_filter( 'woocommerce_package_rates',  'wf_add_charge_if_exceed_cost', 15, 2 );
function wf_add_charge_if_exceed_cost( $available_shipping_methods, $package ){
    
    $mothods  = array('wf_shipping_ups:07','wf_shipping_ups:08'); //Set methods to adjust

    //Config this array with country code, state code and rate to be added.
    $destination_array = array(
        'US' => array(
            'NY' => -0.05,
            'CA' => -0.06,
        ),
        'CA' => array(
            '*' => 0.1,
        )
    );

    global $woocommerce;
    $customer_country = $woocommerce->customer->get_shipping_country();
    $customer_state    = !empty($destination_array[$customer_country]['*']) ? '*' : $package['destination']['state'];

    foreach($mothods as &$current_method) {
        foreach ($available_shipping_methods as $shipping_method => $value) {
            if( strpos( $shipping_method, $current_method ) !== false ) {
                // Cost adjustment
                if ( ! empty( $destination_array[$customer_country][$customer_state] ) ) {
                    $value->cost += $value->cost * floatval( $destination_array[$customer_country][$customer_state] );
                }
            }
        }
    }
    return $available_shipping_methods;
}