some mistake, function disableSub :

..
function disableSub() {
for (var i= 0; i< arguments.length; i++)
checkSub(false, arguments[i]);
}
..

id names (which you are using via document.getElementById(name)) are case sensitive. you named your div with id="NonUS", in your javascript you used ..getElementById("NonUs")..


furthermore, you...

you should better use select and optgroup:


<select name="abc">
<optgroup label="Closely held company">
<option value="..">Sole Proprietor</option>
<option...