I have such a problem on Magento 2.3.3
I checked this logic on stock Magento 2.3.3 and it also appears there.
Choose a 2-3 allowed countries.
Then go to All Customer -> Customer Address Edit Form in Admin area.
Country dropdown is not as we expected.
If I just use 1 country none will show up if you chose more then it will just take countries from the top.
In console i don't have error's.
Anyone had this issue ad anyone solve it?
Best Answer
vendor/magento/module-customer/view/adminhtml/ui_component open customer_address_form.xml and remove below code from line number.194
Remove the above code from the file.