WordPress: Remove parent dropdown selector from hierarchical taxonomy.

functions.php

<?php

function remove_tax_parent_dropdown() {
	$screen = get_current_screen();

	if ( 'region' == $screen->taxonomy ) {
		if ( 'edit-tags' == $screen->base ) {
			$parent = "$('label[for=parent]').parent()";
		} elseif ( 'term' == $screen->base ) {
			$parent = "$('label[for=parent]').parent().parent()";
		}
	} elseif ( 'country' == $screen->post_type ) {
		$parent = "$('#newregion_parent')";
	} else {
		return;
	}

	?>
	<script type="text/javascript">
		jQuery(document).ready(function($) {     
			<?php echo $parent; ?>.remove();       
		});
	</script>
	<?php 
}
add_action( 'admin_head-edit-tags.php', 'remove_tax_parent_dropdown' );
add_action( 'admin_head-term.php', 'remove_tax_parent_dropdown' );
add_action( 'admin_head-post.php', 'remove_tax_parent_dropdown' );
add_action( 'admin_head-post-new.php', 'remove_tax_parent_dropdown' );