My experience this morning.... I wanted to login to my YouTube account to post a video. Typed in my email address, "not recognized". I'm in Canada. So I reload the page, again type in my email after I quadruple check I haven't lost my mind... "not recognized". Did it another 3 or 4 times, not recognized.
Next I logged into the email account that I registered with YouTube and found a few recent messages from YouTube confirming that it was INDEED the correct address. So I wasn't losing my mind, that was the address I registered with for my username on that account.
Next, I decided to completely FLUSH CHROME Cache (delete all history files cookies, etc). Went back to YouTube.... Ok, this time it recognized my username (it didn't immediately say user doesn't exist) and let me input my password. After that, got to a page for 2-factor authentification saying it was going to text my cell phone. HOWEVER, at the top it said too many attempts to login and therefore will wait about 1 hour to allow me to do it again (and I never got the text).

I waited an hour, tried again to log in... it accepted my username no problem, it let me type my password no problem, it then went to the 2-factor authentification page and sent me a code by text that I then typed in, and I was back to the usual.
So something definitely was going on. In Canada. I had no problem viewing YouTube but logging in was an issue, and a strange one at that.