Angular 8 FormArray index data is not updating

I'm trying to create dynamic from groups based on initial data with filled content and add/remove from groups. Unfortunately it is not working.

Expected behavior is,

• Coutry dropdown would be loaded with data and highlighted with selected value which is working fine already.
• Selected country states dropdown data should be loaded by default with selected value from initial data stateCode and when changing the country too which is not working currently.
• While clicking the add button, by default "United states" country and respective states data should be loaded. States dropdown should be selected by default with "--select--".

Note: All data will be coming from API. Testing purpose I have added static objects for Countries and States.

Here my attempt

https://stackblitz.com/edit/angular-8-app-example-fkjzfe-wekubn?file=src%2Fapp%2Fapp.component.ts

Current behaviour demo

https://angular-8-app-example-fkjzfe.stackblitz.io/

HTML

  <form [formGroup]='entityForm'>
              <div formArrayName="optionGroups" class="ui-g ui-g-12 ui-g-nopad " >
                <div  style="width: 100%;
    display: flex; margin-bottom:10px" class="ui-g  ui-g-12 ui-g-nopad " *ngFor="let item of entityForm.controls['optionGroups'].controls; let $index=index" [formGroup]="item">        
                  <div class="ui-md-4">                   
                    <label class="mandatory"
                  >Country
                  <span class="colon"></span>
                </label>
                <select formControlName="country" class="ui-inputtext" (change)="onCountryChange(entityForm.controls['optionGroups'].controls[$index].controls['country'].value, $index)" > 
                  <option>--Select--</option>
                  <option *ngFor="let c of countries" [ngValue]="c.countryCode">{{c.country}}</option>                 
                </select>
              </div>
              <div class="ui-md-4">

                <label class="lbl-hidden"> State </label>
                <select formControlName="state" class="ui-inputtext"> 
                  <option>--Select--</option>
                  <option *ngFor="let state of states[entityForm.controls['optionGroups'].controls[$index].controls['country'].value]" value="state.code">{{state.state}}</option>
              </select>
              </div>
              <div class="ui-md-3">
                <label class="lbl-hidden"> Number </label>
                <input
                  type="text"
                  pInputText
                  class="form-control"
                  formControlName="place"    
                />
                </div>
                <div class="ui-md-1">
                 
                  <button (click)='removeOptionGroup(i)'  style="min-width: auto;"  pButton icon="fa fa-minus">Remove</button>
                </div>
                </div>
              </div>
            </form>        
            <button class="add-remove-btn" pButton (click)='addOptionGroup()' icon="fa fa-plus">Add</button>` 

TS

import { Component, OnInit, ViewChild } from '@angular/core'

import { FormBuilder, Validators, FormArray, FormGroup, FormControl } from '@angular/forms';

@Component({
  selector: 'my-app',
  templateUrl: './app.component.html',
  styleUrls: [ './app.component.css' ]
})
export class AppComponent implements OnInit  {
  public countryOptions:any = [];
  public stateOptions:any = [];

  public countries = [];
  public states = [];

  public entityForm: FormGroup;

constructor(private fb: FormBuilder) {
  this.entityForm = this.fb.group({
    optionGroups : this.fb.array([]),
});

this.countries = this.countryOptions
this.states=[];
}


public addOptionGroup(){

  const fa = this.entityForm.controls["optionGroups"] as FormArray;
   //fa.setValue("--Select--");
  fa.push(this.newOptionGroup());


  }

  public removeOptionGroup(index: number){

    const fa = this.entityForm.controls["optionGroups"] as FormArray;
  
    fa.removeAt(index);
  
    }

    onCountryChange(selectedCountry: string , formIndex : number) : void {
      this.states[selectedCountry] = this.getStates(selectedCountry)
    }

    private newOptionGroup() {
      return new FormGroup({          
          country: new FormControl("--select--"),
          state: new FormControl("--select--"),
          place: new FormControl("GGG"),

      });
  }


  getStates(selectedCountry) {
    //API call

    switch(selectedCountry) {
      case "US" : 
        this.stateOptions =[
      {id: 14, state: "Alabama", code: "AL", countryCode: "US"},
      {id: 15, state: "Alaska", code: "AK", countryCode: "US"},
      {id: 17, state: "Arizona", code: "AZ", countryCode: "US"},
      {id: 18, state: "Arkansas", code: "AR", countryCode: "US"},
      {id: 19, state: "California", code: "CA", countryCode: "US"}
      ]
      break;

     case  "CA" :
       this.stateOptions =[{id: 37, state: "Marshall Islands", code: "MH", countryCode: "CA"},
      {id: 4, state: "New Brunswick", code: "NB", countryCode: "CA"},
      {id: 5, state: "Newfoundland and Labrador", code: "NL", countryCode: "CA"},
      {id: 53, state: "Northern Mariana Islands", code: "MP", countryCode: "CA"},
      {id: 6, state: "Northwest Territories", code: "NT", countryCode: "CA"}]
      break;    
    default: 
     this.stateOptions =[
      {id: 14, state: "Alabama", code: "AL", countryCode: "US"},
      {id: 15, state: "Alaska", code: "AK", countryCode: "US"},
      {id: 17, state: "Arizona", code: "AZ", countryCode: "US"},
      {id: 18, state: "Arkansas", code: "AR", countryCode: "US"},
      {id: 19, state: "California", code: "CA", countryCode: "US"}
      ]
      break;
  }
    return this.stateOptions;

   }

   initFormArray(initForm:any) {
    const formArray = this.entityForm.get('optionGroups') as FormArray;
    initForm.map((item, index) => {
      formArray.push(this.createForms(item, index));
    });
    this.entityForm.setControl('optionGroups', formArray);
   }

   createForms(adresse, index): FormGroup {
   
    let formGroup: FormGroup = new FormGroup(
      {
        country: new FormControl(adresse.countryCode),
        state: new FormControl(adresse.stateCode),
        place: new FormControl(adresse.fileNumber)
      }
    );
 this.onCountryChange(adresse.select1, index)
    return formGroup;
  }


  
 getAllCountries() {
   //API call
   this.countries = [{"country":"United States","countryCode":"US"},{"country":"Canada","countryCode":"CA"}]
 }
  

  ngOnInit() {
    this.getAllCountries()
    const initData = [
      {countryCode: "US", stateCode: "AZ", fileNumber: "AAA"},
      {countryCode: "CA", stateCode: null, fileNumber: null}
    ]

    this.initFormArray(initData)
  }

}