<div id="add_child">
<!-- тут ещё поля, с ними все ок -->
<label>Страна </label>
<select name="country[0]" class="selectpicker countrypicker form-control" data-flag="true" data-default="RU"></select>
</div>
<a href="#" class="add-child-link">Добавить</a>
$(document).on('click', '.add-child-link', function(e){
e.preventDefault();
var newdiv;
newdiv = $('#add_child').clone(true, true).insertBefore(this);
newdiv.removeAttr('id').fadeIn();
});
$(document).on('click', '.add-child-link', function(e){
e.preventDefault();
var newdiv;
newdiv = $('#add_child').clone(true, true).insertBefore(this);
newdiv.find('.selectpicker').data('selectpicker', null);
newdiv.find('.bootstrap-select').find("button:first").remove();
newdiv.find('.selectpicker').selectpicker('val', 'RU');
newdiv.removeAttr('id').fadeIn();
});
var $newRow = $('.js-sizes-row').clone();
$newRow.find('.dropdown-toggle').remove();
$newRow.find('.dropdown-menu').remove();
$newRow.find('select').removeClass('selectpicker');
$newRow.find('.bootstrap-select').removeClass('bootstrap-select');
$newRow.appendTo('.sizes');
$newRow.find('select').selectpicker();