JSFiddle - React, Tailwind, and code Playground

HTML

<input onchange="toggleRegion()" id="ESARO" type="checkbox" class="region"
value="ESARO" name="ESARO">ESARO
    
<br /><br />
    
<input type="checkbox" class="country" value="Afghanistan" name="country2"
/>Afghanistan
<br/>

JavaScript

function toggleRegion() {
    if ($('#ESARO').is(':checked')) {
        $('input[value="Afghanistan"]').attr('checked', true);
    }
}