Create Hiearchical Taxonomy Terms

I’m trying to create hierarchical taxonomy terms on activation of a plugin. I’m just creating 1 parent and 1 child. The terms are being inserted into the database.

My problem is updating the ‘cache’ blogoption that contains the hierachy (children), which gets updated by calling clean_term_cache().

add_action( 'init', 'create_user_location_tax', 0 );
function create_user_location_tax(){
  global $wpdb;
  register_taxonomy( 'location', 'users', array('hierarchical' => true,  'show_ui' => true, 'query_var' => true, 'label' => __('Where are you')) );

  $dummycountry = 'USA';
  $dummystate   = 'KENTUCKY';
  if( taxonomy_exists('location') ){
    $tax_location_terms = get_terms( 'location', 'get=all&hide_empty=false');
    if( count($tax_location_terms) < 1 ){
      $tax_country  = wp_insert_term($dummycountry,  'location');
      $parent       = $tax_country['term_id'];
      $tax_state    = wp_insert_term($dummystate, 'location', array('parent'=>$parent));
      $child        = $tax_state['term_id'];
      clean_term_cache(array($parent), 'location');
    }
  }

  $sql    = "SELECT option_value FROM $wpdb->options WHERE option_name = 'location_children'";
  $result = $wpdb->get_col($sql);
  error_log('term cache: '.$result[0]);
}

Where is the right place to call clean_term_cache()?
How do I store and pass the right IDs to it?