You are looking at the HTML representation of the XML format.
HTML is good for debugging, but is unsuitable for application use.
Specify the format parameter to change the output format.
To see the non HTML representation of the XML format, set format=xml.
See the complete documentation, or API help for more information. 
<?xml version="1.0"?>
<api>
  <query-continue>
    <allfileusages afcontinue="Flag_of_India.png|1537" />
  </query-continue>
  <query>
    <allfileusages>
      <f ns="6" title="File:COL-city icon (2)edited.png" />
      <f ns="6" title="File:COL-city icon (2)edited.png" />
      <f ns="6" title="File:COL-city icon (2)edited.png" />
      <f ns="6" title="File:Canada flag.png" />
      <f ns="6" title="File:Flag of Australia (WFB 2004).gif" />
      <f ns="6" title="File:Flag of Austria.png" />
      <f ns="6" title="File:Flag of Belarus.png" />
      <f ns="6" title="File:Flag of Belgium (WFB 2004).gif" />
      <f ns="6" title="File:Flag of Brazil (WFB 2004).gif" />
      <f ns="6" title="File:Flag of Hungary.svg.png" />
    </allfileusages>
  </query>
</api>