how to handle serialized data with WP_User_Query

I'm trying expand a custom user search in Wordpress; namely, I want to search the users by city, state and country, but these data are serialized. My example

meta_key: pie_address_3;

meta_value: a:6:{s:7:"address";s:18:"New York Street, 4";s:8:"address2";s:0:"";s:4:"city";s:5:"Venice";s:5:"state";s:7:"Vicenza";s:3:"zip";s:5:"36015";s:7:"country";s:5:"Italy";}

Here is what I'm trying to do:

$my_users = new WP_User_Query(
      array( 
        'role' => $role,
        'search' => '*' . $search . '*',
        'search_columns' => array(
            'user_login',
            'user_nicename',
            'user_email',
            'user_url',
            'display_name'
        ),
        'meta_query' => array(
              'key'     => 'pie_address_3',
              'value'   => $search,
              'compare' => 'LIKE'
          )
      ));

But, when I type some country or city (which I know is associated with some user), the search result return nothing. How can I handle this? Thanks!