How do I remove a YouTube app I didn't download?

Open your Applications folder in the Finder and delete it from there.

User > Finder > Applications

Do you see a Chrome apps folder?

Double click it to open and move YouTube to trash if it is there

Hello,

it looks like a software which has nothing to do with youtube or google. Maybe it is a Virus or Software which is not healthy for your computer.

It has a strange Name: "Default blpcfgokakmgncojhhkbfbldkacnbeo".

You should look at /Users/User/x/ if you can find such a file and delete it

Be careful with your data at your Computer. If you can, connect your Mac with Disk-target-mode to another Mac and make a backup.

Did you do a search for youtube or for "blpcfgo..."?

See macOS Sierra: Use Launchpad to view and open apps and macOS Sierra: Install, update, and uninstall apps

Have you tried a Spotlight search and make sure it is looking in "This Mac"? Click on Spotlight icon in the top right of Title menu bar and then type in youtube and then when it shows you the results scroll all the way down on the left to "Show all in Finder" and hopefully will now show you where it is. If that doesn't work do the same for blpcfgo and see if that finds something.

Good luck...

If you click on the "Show Details" button, it will give some more detailed information that might give more clues as to what is going on. Something crashed and the "Show Details" button would give more info about the crash..

Good luck...