// to get users on usermeta,
$user = new WP_User_Query( array( 'meta_key' => 'country', 'meta_value' => 'Israel' ) ); 

To run user query on MagcicMembers member data like sample above, which is saved as serialised array, 
you need to copy the needed metadata to usermeta table, there are now two actions hooks in MGM that allows that.

"mgm_user_options_read" with two arguments, called each time a member object is initialized using mgm_get_member($user_id)
@param array $options
$param int $user_id

"mgm_user_options_save" with two arguments, called each time member object is saved uisng mgm_get_member($user_id)->save();
@param array $options
$param int $user_id

to add any custom meta for query, you need to sync first, this can be achieved by adding a callback to read action
or save action

<code>

/**
 * member object read action, used to copy member data to metadata for easy user query
 * 
 * @param array $options saved in usermeta
 * @param int user_id
 * @return void
 * @since 2.7
 */
function my_user_options_sync_read($options, $user_id){
	// set country if changed	
	if( isset($options['custom_fields']['country']) && !empty($options['custom_fields']['country']) ){
		// check
		if( $options['custom_fields']['country'] != mgm_get_user_option('_mgm_user_country', $user_id)){
			// update
			update_user_option($user_id, '_mgm_user_country', $options['custom_fields']['country'], true);	
		}	
	}
	
	// you can log member options data to inspect how to fetch the data you need
	// this logs to uploads/mgm/logs
	mgm_log($options, ('user_' . $user_id . '_' .__FUNCTION__));
}
// add
add_action('mgm_user_options_read'                      , 'my_user_options_sync_read', 10, 2);

/** 
 * member object write action, used to copy member data to metadata for easy user query
 * 
 * @param array $options saved in usermeta
 * @param int user_id
 * @return void	
 * @since 2.7
 */
function my_user_options_sync_save($options, $user_id){
	// set country if changed	
	if( isset($options['custom_fields']['country']) && !empty($options['custom_fields']['country']) ){
		// check
		if( $options['custom_fields']['country'] != mgm_get_user_option('_mgm_user_country', $user_id)){
			// update
			update_user_option($user_id, '_mgm_user_country', $options['custom_fields']['country'], true);	
		}	
	}
}
// add
add_action('mgm_user_options_save'                      , 'my_user_options_sync_save', 10, 2);

</code>

Now you can run a query on the field

<code>

// to get users on usermeta,
$user = new WP_User_Query( array( 'meta_key' => '_mgm_user_country', 'meta_value' => 'IL' ) ); // IL => Israel

</code>

Note: we suggest you keep a "_mgm_" namespace prefix to all custom meta copied to usermeta, 
this will ensure they do not clash with other internal MGM usermeta as well can be removed 
from the plugin on deactivation.