single select nested array

Summary:

i have done an ADP for countries that shows all the country in the world and bind the data in a single select for 'Country'. my question is, how do i make it so that the other single select ('State' & 'Cities') only appear based on the country.

Also that the data for the states and cities is in nested array and i do not know how to bind the data from nested array to single select. the only method i know is to create type from endpoint and select the strings and not the root array. so data can be bind into the single select from the example of Mr. ShayJDev from youtube -