ENGCOM-5842: Bugfix/22964 #24597

 - Merge Pull Request #24597 from LucasCalazans/magento2:bugfix/22964
 - Merged commits:
   1. 849a267
   2. 4122c40
   3. 140d591
   4. 5d440c5
   5. f51fd0b
   6. c381ae8

Author: magento-engcom-team

app/code/Magento/Checkout/Test/Mftf/Test/StorefrontRegionUpdatesAfterChangingCountryAndLeavingRegionSelectUnselectedTest.xml

@@ -0,0 +1,44 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!--
+ /**
+  * Copyright © Magento, Inc. All rights reserved.
+  * See COPYING.txt for license details.
+  */
+-->
+
+<tests xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+       xsi:noNamespaceSchemaLocation="urn:magento:mftf:Test/etc/testSchema.xsd">
+    <test name="StorefrontRegionUpdatesAfterChangingCountryAndLeavingRegionSelectUnselectedTest">
+        <annotations>
+            <features value="Checkout"/>
+            <stories value="Region updates after changing country "/>
+            <title value="Region updates after changing country "/>
+            <description value="Region dupdates after changing country and leaving region select unselected"/>
+            <severity value="CRITICAL"/>
+            <testCaseId value="https://github.com/magento/magento2/issues/23460"/>
+            <group value="checkout"/>
+        </annotations>
+        <before>
+            <createData entity="Simple_US_Customer" stepKey="createCustomer"/>
+        </before>
+        <after>
+            <deleteData createDataKey="createCustomer" stepKey="deleteCustomer"/>
+        </after>
+
+        <!-- Login to storefront from customer -->
+        <actionGroup ref="LoginToStorefrontActionGroup" stepKey="loginCustomer">
+            <argument name="Customer" value="$$createCustomer$$"/>
+        </actionGroup>
+
+        <actionGroup ref="StorefrontOpenMyAccountPageActionGroup" stepKey="goToMyAccountPage"/>
+
+        <actionGroup ref="StorefrontCustomerGoToSidebarMenu" stepKey="goToAddressBookPage">
+            <argument name="menu" value="Address Book"/>
+        </actionGroup>
+        <actionGroup ref="StoreFrontClickEditDefaultShippingAddressActionGroup" stepKey="clickEditAddress"/>
+        <selectOption selector="{{StorefrontCustomerAddressFormSection.country}}" userInput="{{updateCustomerFranceAddress.country}}" stepKey="selectCountry"/>
+        <actionGroup ref="AdminSaveCustomerAddressActionGroup" stepKey="saveAddress"/>
+
+        <see selector="{{StorefrontCustomerAddressesSection.defaultShippingAddress}}" userInput="{{updateCustomerFranceAddress.country}}" stepKey="seeAssertCustomerDefaultShippingAddressCountry"/>
+    </test>
+</tests>

app/code/Magento/Checkout/view/frontend/web/js/region-updater.js

@@ -162,6 +162,9 @@ define([
             this._clearError();
             this._checkRegionRequired(country);
 
+            $(regionList).find('option:selected').removeAttr('selected');
+            regionInput.val('');
+
             // Populate state/province dropdown list if available or use input box
             if (this.options.regionJson[country]) {
                 this._removeSelectOptions(regionList);

app/code/Magento/Customer/Test/Mftf/ActionGroup/StoreFrontClickEditDefaultShippingAddressActionGroup.xml

@@ -0,0 +1,19 @@
+<?xml version="1.0" encoding="UTF-8"?>
+    <!--
+     /**
+      * Copyright © Magento, Inc. All rights reserved.
+      * See COPYING.txt for license details.
+      */
+    -->
+
+<actionGroups xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+              xsi:noNamespaceSchemaLocation="urn:magento:mftf:Test/etc/actionGroupSchema.xsd">
+<actionGroup name="StoreFrontClickEditDefaultShippingAddressActionGroup">
+    <annotations>
+        <description>Click on the edit default shipping address link.</description>
+    </annotations>
+
+    <click stepKey="ClickEditDefaultShippingAddress" selector="{{StorefrontCustomerAddressesSection.editDefaultShippingAddress}}"/>
+    <waitForPageLoad stepKey="waitForStorefrontSignInPageLoad"/>
+</actionGroup>
+</actionGroups>