/**
 * Implements hook_field_widget_form_alter().
 */
function MYMODULE_field_widget_form_alter(&$element, $form_state, $context) {
  if(!empty($element['#addressfield'])) {
    $element['country']['#weight'] = 100;
  }
}

/**
 * Implements hook_ctools_plugin_directory().
 */
function MYMODULE_ctools_plugin_directory($module, $plugin) {
  if ($module == 'addressfield') {
    return 'plugins/' . $plugin;
  }
}

/**
 * Implements hook_ctools_plugin_type().
 */
function MYMODULE_ctools_plugin_type() {
  $plugins['format'] = array(
    'load themes' => TRUE,
  );
  return $plugins;
}

/**
 * @file
 * Move country field to the very end.
 */

$plugin = array(
  'title' => t('Alter addressfield'),
  'format callback' => 'MYMODULE_format_address_alter_country',
  'type' => 'address',
  'weight' => -80,
);

/**
 * Format callback.
 *
 * @see CALLBACK_addressfield_format_callback()
 */
function MYMODULE_format_address_alter_country(&$format, $address, $context = array()) {
  // Move country field to the very end.
  $format['country']['#weight'] = 100;
}