code: protected function didInvoiceCountryChanged(SaleInterface $sale)
      {
          $saleCs = $this->persistenceHelper->getChangeSet($sale);
  
          // Watch for invoice country change
          $oldCountry = $newCountry = null;
  
          $oldAddress = isset($saleCs['invoiceAddress']) ? $saleCs['invoiceAddress'][0] : $sale->getInvoiceAddress();
          if (null !== $oldAddress) {
              $oldAddressCs = $this->persistenceHelper->getChangeSet($oldAddress);
              $oldCountry = isset($oldAddressCs['country']) ? $oldAddressCs['country'][0] : $oldAddress->getCountry();
          }
  
          // Resolve the new tax resolution target country
          if (null !== $newAddress = $sale->getInvoiceAddress()) {
              $newCountry = $newAddress->getCountry();
          }
  
          if ($oldCountry !== $newCountry) {
              return true;
          }
  
          return false;
      }
docs: Returns whether the invoice address has changed.
  
  @param SaleInterface $sale
  
  @return bool