Display a tag before the menu list content

Put this function into your theme’s function.php file.

function is_tree($pid) { // $pid = The ID of the page we're looking for pages underneath
    global $post;
    $anc = get_post_ancestors( $post->ID );
    foreach($anc as $ancestor) {
            if(is_page() && $ancestor == $pid) {
                    return true;
            }
    }
    if(is_page()&&(is_page($pid))) { return true; /*we're at the page or at a sub page*/ }
    else { return false; /*we're elsewhere*/ }
}

Then wrap your code in:

<?php
  // put the parent id or in this case, South America's id as the parent-id
  if(is_tree('parent-id')) {
    // output your menu
  }
?>