How to block scripts

Using cookiebot I get this report (one example below).

VISITOR_INFO1_LIVE youtube.com HTTP 179 days
First found URL: https://mywebsite.com/
Cookie purpose description: Tries to estimate the users’ band width on pages with integrated YouTube videos.
Initiator: Script tag, page source line number 383
Source: https://www.youtube.com/iframe_api
via https://mywebsite.com/wp-includes/js/wp-custom-header.min.js?ver=5.8.1
Data is sent to: United States (not adequate)
Blocked until accepted by user: No

As far as I’m aware no plugin/video used on site. Certainly no scripts added to the header (the only example you give re adding a script is GA, and this is manually added to the site’s header, so makes perfect sense).

My question is how do you locate scripts found by your scanner that you haven’t yourself added to the header of your theme?

Do I have to use something like cookiebot then from the report it produces use initiator line number and source information (above) to locate and then add the scripts of those cookies in the non-necessary cookie script input field in your plugin settings.

But how do I then delete the script in the source code if in a file loaded by a plug-in/embed?

Totally confused, probably my lack of understanding. Many thanks.