We are indeed using the Address module, thanks for the thought. But, on a clean install of Drupal with Webform and Address installed, modifying the CountryManager's $countries array is still reflected in a test Webform
Eg:
I can report the same error; I'm also on Drupal 9.5.
[13-Sep-2023 22:53:59 UTC] ArgumentCountError: Too few arguments to function Drupal\mail_login\AuthDecorator::__construct(), 3 passed in /var/www/html/docroot/core/lib/Drupal/Component/DependencyInjection/Container.php on line 259 and exactly 5 expected in /var/www/html/docroot/modules/contrib/mail_login/src/AuthDecorator.php on line 69 #0 /var/www/html/docroot/core/lib/Drupal/Component/DependencyInjection/Container.php(259): Drupal\mail_login\AuthDecorator->__construct()
#1 /var/www/html/docroot/core/lib/Drupal/Component/DependencyInjection/Container.php(177): Drupal\Component\DependencyInjection\Container->createService()
#2 /var/www/html/docroot/core/modules/user/src/Form/UserLoginForm.php(95): Drupal\Component\DependencyInjection\Container->get()
#3 /var/www/html/docroot/core/lib/Drupal/Core/DependencyInjection/ClassResolver.php(28): Drupal\user\Form\UserLoginForm::create()
#4 /var/www/html/docroot/core/lib/Drupal/Core/Form/FormBuilder.php(195): Drupal\Core\DependencyInjection\ClassResolver->getInstanceFromDefinition()
#5 /var/www/html/docroot/core/lib/Drupal/Core/Form/FormBuilder.php(232): Drupal\Core\Form\FormBuilder->getFormId()
#6 /var/www/html/docroot/core/lib/Drupal/Core/Form/FormBuilder.php(224): Drupal\Core\Form\FormBuilder->buildForm()
#7 /var/www/html/docroot/themes/my_theme/my_theme.theme(71): Drupal\Core\Form\FormBuilder->getForm()
#8 [internal function]: my_theme_preprocess_node()
#9 /var/www/html/docroot/core/lib/Drupal/Core/Theme/ThemeManager.php(287): call_user_func_array()
#10 /var/www/html/docroot/core/lib/Drupal/Core/Render/Renderer.php(433): Drupal\Core\Theme\ThemeManager->render()
#11 /var/www/html/docroot/core/lib/Drupal/Core/Render/Renderer.php(204): Drupal\Core\Render\Renderer->doRender()
#12 /var/www/html/docroot/core/lib/Drupal/Core/Render/MainContent/HtmlRenderer.php(242): Drupal\Core\Render\Renderer->render()
#13 /var/www/html/docroot/core/lib/Drupal/Core/Render/Renderer.php(580): Drupal\Core\Render\MainContent\HtmlRenderer->Drupal\Core\Render\MainContent\{closure}()
#14 /var/www/html/docroot/core/lib/Drupal/Core/Render/MainContent/HtmlRenderer.php(243): Drupal\Core\Render\Renderer->executeInRenderContext()
#15 /var/www/html/docroot/core/lib/Drupal/Core/Render/MainContent/HtmlRenderer.php(132): Drupal\Core\Render\MainContent\HtmlRenderer->prepare()
#16 /var/www/html/docroot/core/lib/Drupal/Core/EventSubscriber/MainContentViewSubscriber.php(90): Drupal\Core\Render\MainContent\HtmlRenderer->renderResponse()
#17 [internal function]: Drupal\Core\EventSubscriber\MainContentViewSubscriber->onViewRenderArray()
#18 /var/www/html/docroot/core/lib/Drupal/Component/EventDispatcher/ContainerAwareEventDispatcher.php(142): call_user_func()
#19 /var/www/html/docroot/vendor/symfony/http-kernel/HttpKernel.php(174): Drupal\Component\EventDispatcher\ContainerAwareEventDispatcher->dispatch()
#20 /var/www/html/docroot/vendor/symfony/http-kernel/HttpKernel.php(81): Symfony\Component\HttpKernel\HttpKernel->handleRaw()
#21 /var/www/html/docroot/core/lib/Drupal/Core/StackMiddleware/Session.php(58): Symfony\Component\HttpKernel\HttpKernel->handle()
#22 /var/www/html/docroot/core/lib/Drupal/Core/StackMiddleware/KernelPreHandle.php(48): Drupal\Core\StackMiddleware\Session->handle()
#23 /var/www/html/docroot/core/modules/page_cache/src/StackMiddleware/PageCache.php(191): Drupal\Core\StackMiddleware\KernelPreHandle->handle()
#24 /var/www/html/docroot/core/modules/page_cache/src/StackMiddleware/PageCache.php(128): Drupal\page_cache\StackMiddleware\PageCache->fetch()
#25 /var/www/html/docroot/core/modules/page_cache/src/StackMiddleware/PageCache.php(82): Drupal\page_cache\StackMiddleware\PageCache->lookup()
#26 /var/www/html/docroot/core/modules/ban/src/BanMiddleware.php(50): Drupal\page_cache\StackMiddleware\PageCache->handle()
#27 /var/www/html/docroot/core/lib/Drupal/Core/StackMiddleware/ReverseProxyMiddleware.php(48): Drupal\ban\BanMiddleware->handle()
#28 /var/www/html/docroot/core/lib/Drupal/Core/StackMiddleware/NegotiationMiddleware.php(51): Drupal\Core\StackMiddleware\ReverseProxyMiddleware->handle()
#29 /var/www/html/docroot/vendor/stack/builder/src/Stack/StackedHttpKernel.php(23): Drupal\Core\StackMiddleware\NegotiationMiddleware->handle()
#30 /var/www/html/docroot/core/lib/Drupal/Core/DrupalKernel.php(718): Stack\StackedHttpKernel->handle()
#31 /var/www/html/docroot/index.php(19): Drupal\Core\DrupalKernel->handle()
#32 {main} request_id="v-6cfcba98-5288-11ee-9e20-8302e64bd82a"