I cannot uninstall Ubercart. I have installed a fresh blank copy of Drupal and Ubercart 8.x-4.x-dev and I can reproduce the issue.
Installed Cart, Country, Order, Product, and Store.
When Uninstalling Country I get
RouteNotFoundException: "Route "entity.uc_country.collection" does not exist." at /[DrupalPath]/core/lib/Drupal/Core/Routing/RouteProvider.php line 187