TBH I'm not aware of any site, which would allow me to delete the account without logging in.
Facebook´ has only instructions with links https://www.facebook.com/help/224562897555674
Google: When I visit the page as guest, I'm also getting only instructions and links which result in the login form or even more instructions/information but no way to delete an account, if I visit them without logging in: https://support.google.com/accounts/answer/32046?hl=en
It's kind of logical, isn't it?:D It would be really stupid if one could ask them to get deleted, without logging in to make sure that it's really me.