$(document).ready(function(){
// This is when this select is selected, it opens the country select.
$('#country').on('change',function(){
$("#other").css("display","block");
});
// First, lets check if the dropdown has an onChange that took place
$('#other').on('change',function(){
// Store the value of the selected option into a variable
var selectedCountry = $("#other option:selected").val();
// If that option is 1, then we make the button block so it appears, we change the href link to your desired URL as well as change the text for that button. You can remove whichever feature you don't want.
if(selectedCountry==1) {
$("#cart").css("display","block");
$("#cart").attr("href", "#");
$("#cart").html('Add To Cart - Singapore');
}
// Use else if if the option is 2, then do the following as mentioned above.
else if(selectedCountry==2) {
$("#cart").css("display","block");
$("#cart").attr("href", "#");
$("#cart").html('Add To Cart - USA');
} else {
// If its not 1 or 2, then make button disappear again , so that when someone clicks on an option and deciddes to go back to default Please select option, the add to cart will disappear.
$("#cart").css("display","none");
}
});
});
#cart {
display: none;
}
#other {
display: none;
}
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<select id="country">
<option value="0">Please Select</option>
<option value="1">Singapore</option>
<option value="2">USA</option>
</select>
<select id="other">
<option value="0">Please Select</option>
<option value="1">Test 1</option>
<option value="2">Test 2</option>
</select>
<button id="cart"></button>