function add_post_content($content) {
 if(!is_feed() && !is_home()) {
 $meta = get_post_meta( get_the_ID(), 'usp_custom_field', true );
 $content .= '<p>[pw_map address="'.$meta.'" key="AIzaSyD1J47nUjdDU1e9l75vq8hHzR9jKRrxAU8"]</p>';
 }
 return $content;
}
add_filter('the_content', 'add_post_content');