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="Back_in_the_fight1.png|17256" />
  </query-continue>
  <query>
    <allfileusages>
      <f ns="6" title="File:B-29 party favor icon1.jpg" />
      <f ns="6" title="File:B-29 party favor icon1.jpg" />
      <f ns="6" title="File:B-line medal1.png" />
      <f ns="6" title="File:B-line trauma icon1.jpg" />
      <f ns="6" title="File:B-line trauma icon1.jpg" />
      <f ns="6" title="File:Babylon91911.jpg" />
      <f ns="6" title="File:Babylon91911.jpg" />
      <f ns="6" title="File:Babylon91911.jpg" />
      <f ns="6" title="File:Babylon 9191 icon1.jpg" />
      <f ns="6" title="File:Back in action medal1.png" />
    </allfileusages>
  </query>
</api>