How to save post change url youtube link?

I think you want to change default video width.
You can change default embed video width and height by embed_defaults filter.

add_filter('embed_defaults', 'ravs_embed_defaults');

function ravs_embed_defaults($embed_size) {
    if (is_single()) { // Conditionally set max height and width
        $embed_size['width'] = 640;
        $embed_size['height'] = 600;
    } else {           // Default values
        $embed_size['width'] = 460;
        $embed_size['height'] = 600;
    }
    return $embed_size; // Return new size
}