优化

app/code/Magento/Checkout/Block/Cart/Shipping.php

@@ -44,6 +44,7 @@ class Shipping extends \Magento\Checkout\Block\Cart\AbstractCart
      */
     private $jsonHexTagSerializer;
 
+    protected $_quote;
     /**
      * @param Context $context
      * @param CustomerSession $customerSession
@@ -55,6 +56,7 @@ class Shipping extends \Magento\Checkout\Block\Cart\AbstractCart
      * @param JsonHexTag|null $jsonHexTagSerializer
      * @throws \RuntimeException
      */
+
     public function __construct(
         Context $context,
         CustomerSession $customerSession,
@@ -67,6 +69,7 @@ class Shipping extends \Magento\Checkout\Block\Cart\AbstractCart
     ) {
         $this->configProvider = $configProvider;
         $this->layoutProcessors = $layoutProcessors;
+        $this->_quote = $checkoutSession->getQuote();
         parent::__construct($context, $customerSession, $checkoutSession, $data);
         $this->_isScopePrivate = true;
         $this->serializer = $serializer ?: ObjectManager::getInstance()->get(Json::class);
@@ -83,7 +86,10 @@ class Shipping extends \Magento\Checkout\Block\Cart\AbstractCart
     {
         return $this->configProvider->getConfig();
     }
-
+    public function getCountryId() {
+        $shippingAddress = $this->_quote->getShippingAddress();
+        return $shippingAddress->getCountryId();
+    }
     /**
      * Retrieve serialized JS layout configuration ready to use in template
      *

app/code/Magento/Checkout/view/frontend/templates/cart/shipping.phtml

@@ -7,7 +7,9 @@
 ?>
 <?php /** @var $block \Magento\Checkout\Block\Cart\Shipping */ ?>
 <?php /** @var \Magento\Framework\View\Helper\SecureHtmlRenderer $secureRenderer */ ?>
-
+<?php
+$selectedCountryId = $block->getCountryId();
+?>
 <div id="block-shipping" class="block shipping">
     <div id="block-summary" style="display: none;">
         <form method="post" id="shipping-zip-form">
@@ -41,5 +43,10 @@
 script;
         ?>
         <?= /* @noEscape */ $secureRenderer->renderTag('script', [], $scriptString, false) ?>
+        <script>
+            require(['jquery'], function($) {
+                $('#shipping_country_id').val('<?= $selectedCountryId?>');
+            });
+        </script>
     </div>
 </div>

app/code/Magento/Checkout/view/frontend/web/js/view/address-get.js

@@ -18,6 +18,7 @@ define([
             this._super();
             var address={};
             address.countryId = window.checkoutConfig.defaultCountryId;
+            address.postcode = window.checkoutConfig.postcode;
             getAddress.getRates(address);
 
         }