When I run your code, I get a javascript error in Chrome:
Refused to execute script from 'https://www.googleapis.com/fusiontables/v1/query?sql=SELECT%20*%20FROM%20XXXXXXX&key=XXXXXXX' because its MIME type ('application/json') is not executable, and strict MIME type checking is enabled.
You are missing the "callback=handler" parameter in your query (from the example you quote).
Once I fix that your parsing routine is not correct for the data returned, there is no items property of the response. This works for me:
<html>
<head>
<title>Google Fusion Tables API Example</title>
</head>
<body>
<div id="content"></div>
<script>
function handler(response) {
var contentStr = "<table>";
for (var i = 0; i < response.rows.length; i++) {
var item = response.rows[i];
contentStr += "<tr>";
for (var j = 0; j < item.length; j++) {
contentStr += "<td>" + item[j]+"</td>";
}
contentStr += "</tr>";
}
contentStr += "</table>";
document.getElementById("content").innerHTML = contentStr;
}
</script>
<script src="https://www.googleapis.com/fusiontables/v1/query?sql=SELECT%20*%20FROM%20XXXXX=XXXXXX&callback=handler"></script>
</body>
</html>