Google Maps API V3 KML layer does not show up

Question 1

There are 3 issues I see:

the initialize function is never called
the map has no size

the KML is not valid (returns status INVALID_DOCUMENT)

<!DOCTYPE html>
<html>
<head>
<script src="https://maps.googleapis.com/maps/api/js?v=3.exp&sensor=false">
</script>

<script>
function initialize()
{
var mapOptions = {
    center: new google.maps.LatLng(38,-79.5),
    zoom:3,
    mapTypeId: google.maps.MapTypeId.TERRAIN
 }
var map=new google.maps.Map(document.getElementById("googleMap"),mapOptions);
var overlay = new google.maps.KmlLayer('https://doc-08-4g-docs.googleusercontent.com/docs/securesc/ckoh7mm1pf9l58sknv61gkpp19v37j15/r3rh37mucb8nscl1r37disrlcom7i93t/1372536000000/00236509183910004089/00236509183910004089/0B-qVNYv_qM5vNy1ZbzJYVUgtTjA?h=16653014193614665626&e=download');

overlay.setMap(map);
google.maps.event.addListener(overlay,'status_changed',function(){
  document.getElementById('status').innerHTML = overlay.getStatus();
});
  }
google.maps.event.addDomListener(window,'load', initialize);
</script>
</head>
<body>
<div id="googleMap" style="height:500px;width:600px;"></div>
<div id="status"></div>
</body>
</html>

Question 2

google maps javascript API, KML layer, limit the KML size to 10MB. Over 10MB, you will get invalid document status on kmllayer object.

Your KML must first load to google KML service, than return back the tiled image to you. Therefore your KML size must less than 10MB.

https://developers.google.com/maps/documentation/javascript/kmllayer#restrictions