JSFiddle - React, Tailwind, and code Playground

HTML

<link rel="stylesheet" href="http://maxcdn.bootstrapcdn.com/bootstrap/3.3.5/css/bootstrap.min.css">
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.3/jquery.min.js"></script>
<script src="http://js.nicdn.de/bootstrap/formhelpers/docs/assets/js/bootstrap-formhelpers-countries.en_US.js"></script>
<script src="http://js.nicdn.de/bootstrap/formhelpers/docs/assets/js/bootstrap-formhelpers-countries.js"></script>
<script src="http://js.nicdn.de/bootstrap/formhelpers/docs/assets/js/bootstrap-formhelpers-states.en_US.js"></script>
<script src="http://js.nicdn.de/bootstrap/formhelpers/docs/assets/js/bootstrap-formhelpers-states.js"></script>
<link rel="stylesheet" href="http://js.nicdn.de/bootstrap/formhelpers/docs/assets/css/bootstrap-formhelpers.css">
    
<form>
    <label>Country *</label>
    <select id="countries" class="form-control bfh-countries"></select>
    <label>State</label>
    <select id="states" class="form-control bfh-states" data-country="countries"></select>
</form>
<br>
<button onclick="test()" class="btn">Load Country</button>

JavaScript

function test(){
    document.getElementById('countries').value = "AU";
    //I've tried this also
     //$('#countries').bfhcountries({country: 'AU'});
    //$('#states').bfhstates({country: 'AU', state: 'NSW'});
}