app/code/Magento/Backend/etc/adminhtml/system.xml

...to/ConfigurableProduct/Model/Product/VariationHandler.php

...eProduct/Test/Unit/Model/Product/VariationHandlerTest.php

app/code/Magento/Customer/Model/Customer/DataProvider.php

app/code/Magento/Customer/Model/Plugin/AllowedCountries.php

.../Model/ResourceModel/Address/Attribute/Source/Country.php

...rceModel/Address/Attribute/Source/CountryWithWebsites.php

app/code/Magento/Customer/Setup/UpgradeData.php

...to/Customer/Test/Unit/Model/Customer/DataProviderTest.php

.../Customer/Test/Unit/Model/Plugin/AllowedCountriesTest.php

...odel/Address/Attribute/Source/CountryWithWebsitesTest.php

app/code/Magento/Customer/etc/di.xml

app/code/Magento/Customer/etc/module.xml

...Magento/Customer/view/base/ui_component/customer_form.xml

app/code/Magento/Directory/Model/AllowedCountries.php

...ento/Directory/Model/ResourceModel/Country/Collection.php

...agento/Directory/Test/Unit/Model/AllowedCountriesTest.php

...gento/Sales/Block/Adminhtml/Order/Create/Form/Address.php

.../Magento/Ui/view/base/web/js/dynamic-rows/dynamic-rows.js

app/code/Magento/Ui/view/base/web/js/form/element/country.js