You cannot download a video that YouTube has physically deleted from its servers due to a copyright strike. If the message says "Removed due to copyright claim," the file is gone. If it says "Blocked in your country," the file remains accessible via proxy.
Downloading YouTube videos that have been blocked due to copyright is a complex process because it involves bypassing both technical restrictions and legal protections. Understanding Why Videos are Blocked YouTube uses a system called Content ID how to download blocked youtube videos copyright
If you're interested in a specific video, you can try contacting the copyright holder or the video uploader to request permission to download or use the video. You cannot download a video that YouTube has